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France
Cold War
  
EE-2
French clandestine plug-in transmitter - type 2

EE-2 1 is a miniature clandestine short-wave plug-in transmitter that 'steals' its power from a valve (tube) socket of a contemporary broadcast receiver, developed around 1954 by or for the French intelligence service in Berlin (Germany) — the DR/SR. 2 It was the successor to the EE-1 and was used into the 1960s for agent-to-centre communication across the Iron Curtain in Cold War East-Germany [1]. It comprises a single valve oscillator, of which two versions are known.

The device measures 223 x 103 x 34 mm and weights just 530 grams. Unlike its predecessor – the EE-1 – it does not have a built-in morse key.

Instead, a regular morse key must be connected to the banana sockets at the right hand side of the device. The other banana sockets are used for the power supply, which is taken from the socket of the audio frequency (AF) valve of a regular broadcast receiver of the era, using the supplied power cable. At the end of the cable is a plug which can be fitted to the socket of the receiver's AF valve, commonly a 9-pin EL84. 3
  
French plug-in transmitter Type 2 (EE-2)

According to surviving documents of the former East-German MfS (Stasi) [3], EE-2 devices were thought to have been developed in 1954 and were confiscated regularly between 1956 and 1957. They were found with a morse slide pad – like the one found with a BCRA transmitter – instead of a regular morse key. From 1957 onwards, the morse slide pad was replaced by a wind-up tape player that acted as a burst transmitter (see below) [5]. It is unknown how many EE-2 units were manufactured, but judging from the professional build style, it was factory produced in series.

  1. As the official designator of this transmitter is currently unknown, we have nicknamed it EE-2, which is short for Émetteur Enfichable type 2 (plug-in transmitter type 2).
  2. During the Cold War, DR/SR was the French intelligence service in Berlin. It was part of the Sûreté National (SN) and was responsible for army, air force, political and economic espionage against East Germany and the MfS (Stasi). It equipped its agents with motor cycles and clandestine radios [7][8].
  3. Cables for other valve types have been spotted as well, such as for P-type sockets (see below).

PLEASE HELP — Crypto Museum are still looking for additional information about this transmitter. Please help us to expand this page by providing information about the development of this device. Where and when was it designed, and what was the official designator? We would also like to hear stories from people who have worked with this device. If you have any information, please contact us.
French plug-in transmitter Type 2 (EE-2)
Front panel with engraved lettering
Right side with banana sockets
Power connections on the right side
Crystal installed in the XTAL socket
Connections at the right side
Transmitter outside its case shell
Complete setup
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French plug-in transmitter Type 2 (EE-2)
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Front panel with engraved lettering
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Right side with banana sockets
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Power connections on the right side
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Crystal installed in the XTAL socket
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Connections at the right side
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Transmitter outside its case shell
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Complete setup

Features
The image below shows what a complete setup might have looked like. The transmitter takes its power from a domestic broadcast receiver of the era, and is connected to the socket of the EL84 valve in the receiver's AF stage via a 3-wire cable with a noval plug at one end. To avoid mistakes, coloured banana plugs are used, which should match the coloured dots at the top surface. For high-speed transmissions in morse code, either a morse slide pad was provided or a tape-based burst encoder. The frequency is determined by one of 15 crystals in the 4-10 MHz range.

Click to see more

Antenna and counterpoise (ground) should be connected to the transmitter's front panel. The wires for this were usually supplied on a pertinax (paxolin) card. The ground wire has a crocodile clip at the end, which allows it to be connected to the metal pipes of the water supply or heating. Note that the text on the iron body of the transmitter and on the front panel, is engraved rather than screen printed. Due to rust, the engravings may have deteriorated somewhat.

Versions
At least two versions of this transmitter are known, which we will call Mark I and Mark II:

  • Mark I
    This is the simplest version of the transmitter, of which the circuit diagram is presented below. It is believed that this is the earliest version of the device. The transmitter featured here is of this type.

  • Mark II
    This version is cosmetically identical to the Mark I, but is internally somewhat different. Although it is very similar to the Mark I, there are various improvements to the circuit, probably to make the transmitter more stable. It is believed that this is a later version. Photographs of this version can be found in Louis Meulstee's Wireless for the Warrior [1].
Parts
Plug-in transmitter type 2
TX
Morse entry pad with slide contact
Tape-based burst encoder/transmitter
Power cable for EL84 socket
Quarz Crystals
Wire antenna and counterpoise
Transmission schedule with time and frequencies
Transmitter
The transmitter is the heart of the clandestine station. It is housed in metal enclosure that measures 223 × 103 × 34 mm and weights 530 grams. the enclosure consists of a frame, attached to the front panel, and a removable shell. At the right side are banana sockets for connection of the power supply and a morse key. The sockets for connection of an antenna and a suitable counterpoise are at the front panel.

 Look inside the transmitter

  
French plug-in transmitter Type 2 (EE-2)

Morse slide pad
For quick transmission of morse numbers, whithout knowledge of morse code, this small contact pad was issued, It consists of six slots with intermittendly coded contacts, and a slide contact. By moving the slide contact through one of the slots, the corresponding number is sent.

The slide pad shown here is very similar to the one issued with the EE-2, and was found with a French BCRA transmitter.

 More information

  
Morse slide pad with cable

Morse burst encoder   wanted item
Around 1957 the morse slide pad was replaced by the tape player shown in the image on the right. It allowed a pre-recorded message to be sent as a 'burst' in just a few seconds. It not only reduced mistakes, but also the 'on-air' time, thereby minimising the chance of being captured by means of Radio Direction Finding (RDF).

The device shown here was captured by the Stasi in the former DDR [5][9].

 Other burst encoders

  
French burst encoder from the collection of the Stasi Traditionskabinett (now in DHM). Photograph by Detlev Vreisleben [2].

Power cable for EL84 socket
Power for the transmitter was usually 'borrowed' from a regular broadcast receiver. In most cases, a cable was supplied that could be fitted to the 9-pin socket of the EL84 valve that was present in the audio frequency (AF) stage of the receiver.

Cables for this socket type were found with the EE-2 transmitters that were confiscated in the DDR in the late 1950s and early 1960s. The image on the right shows a functional reproduction of the cable and the plug.

 Cable wiring for EL84 socket

  
Power cable for EL84 socket

Power cable for P-socket
The transmitter featured on this page, was found in 2022 with the short power cable shown in the image on the right. It has three colour-coded banana plugs at one end (red, green and black), and a P-type plug-and-socket at the other end.

It is uncertain whether this was an originally issued cable or a homemade add-on by a previous owner, but it allows power to be 'borrowed' from any receiver that has valves with P-type sockets, such as the EL3, EL6 and EF6.

 Cable wiring for P-type socket

  
Power cable for P-type valve socket

Quarz crystals
The transmitters can only be used with quarz crystals in the range 4 to 10 MHz, oscillating in parallel resonance at their ground frequency. A set of 15 black crystals was usually supplied with the transmitter. The required frequency was taken from the transmission schedule [5].

The pins are 2.35 mm thick and are 12.34 mm apart. Suitable enclosures are HC-17/U (HC-6/L), FT-241 and FT-243.

 List of the 15 crystals
 More about crystals

  
Crystals

Antenna
At the front panel of the transmitter are two banana sockets: an isolated one for connection of a wire antenna and a non-isolated one for a suitable counterpoise (ground). The wire antenna should be long enough to allow the transmitter to be tuned effectively. In most cases a 20 metre wire will be sufficient.

The counterpoise could be formed by a similar long wire, but could also be obtained from existing grounded grids, such as the water supply or heating pipes.

  
Wire antenna

Transmission schedule
Each agent was given a transmission schedule that listed the times and frequencies for each day of the month. The agent used this schedule when sending information to the Centre.

The schedule also listed the daily times and frequencies of the broadcasts of the Centre. A complete transmission schedule was obtained by the Stasi in the East-Germany in 1961, on double agent DAHLIE [5].

 Description of the schedule
 Transcribed copy

  
Click to see more

French plug-in transmitter Type 2 (EE-2)
Morse slide pad with cable
Morse slide pad
Operating the slide pad
Crystals
Power cable for P-type valve socket
Power cable for P-type valve socket
Wire antenna
Power cable for EL84 socket
Power cable and cable for connection to external power supply
Noval 9-pin plug
Noval plug and socket
French burst encoder from the collection of the Stasi Traditionskabinett (now in DHM). Photograph by Detlev Vreisleben [2].
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French plug-in transmitter Type 2 (EE-2)
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Morse slide pad with cable
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Morse slide pad
B
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Operating the slide pad
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Crystals
B
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Power cable for P-type valve socket
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Power cable for P-type valve socket
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Wire antenna
B
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Power cable for EL84 socket
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Power cable and cable for connection to external power supply
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Noval 9-pin plug
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Noval plug and socket
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French burst encoder from the collection of the Stasi Traditionskabinett (now in DHM). Photograph by Detlev Vreisleben [2].

Obtained by the Stasi
The French plug-in transmitter was issued to agents (civilians) in the DDR (East-Germany) who were spying for the French. Both the EE-2 and its predecessor, the EE-1, were confiscated on several occasions. In at least one case in 1961, an EE-2 was obtained by the Sasi, complete with the tape-based high speed burst transmitter shown in the image below. It replaced the manual morse slide pad [5]. The set was obtained through double agent DAHLIE (Wolfgang Herrschaft), who was recruited by French intelligence, but was in reality a secret employee (GM) of the Stasi.

Digitally enhanced photographs extracted from Stasi file of September 1961 [5]

The photograph above was extracted from a Stasi file of September 1961 [5]. It shows a white 3-wire cable with three banana plugs at one end, and a 9-pin noval plug at the other. It mates with the socket of an EL84 valve in the receiver. A photograph of the EE-2 with the slide pad, and another one of a third variant concealed as a camera (EE-3), can be found in another Stasi file [6].

 Read the full Stasi file


Burst transmitter
The burst encoder (also known as burst transmitter or burst keyer) is about the same size as the transmitter itself, but thicker. It contains two spools with a metal tape that is driven by a spring-loaded mechanism. The mechanism can be wound up by means of a key, much like a clock [9].

Opened burst encoder with key to wind up the spring-loaded mechanism [9]

The message is recorded on the tape by means of nail polish in the form of narrow lines, wide lines, narrow spaces and wide spaces, similar (but not identical) to morse code. For this purpose, 10 templates are provided that represent the numbers 0-9. Once the message is complete, the spools are installed in the playback mechanism and the wound-up spring is released. It is likely that the tape is sensed electrically, assuming that the applied nail polish acts as an isolator.

Templates for applying nail polish to the metal tape [9]

The result is a high-speed pattern of short and long beeps and spaces that is broadcast by the transmitter on a frequency in the short wave band. At the Centre it is first recorded and then played back at lower speed, so that it could be transcribed. It is likely that the latter was done with the help of an undulator or an automated device that could recognise the patterns.


Transmission schedule
Apart from a transmitter and a morse code device, each agent received a set of 15 different quarz crystals for frequencies in the 4 to 10 MHz range. The agent also received a schedule that defined the hour, minute and frequency for transmission on a given day. It is likely that this schedule was different for each agent. Below is the transmission schedule that landed in the hands of the Stasi in 1961, through double agent 'DAHLIE' — the cover name of Wolfgang Herrschaft (see above) [5].

Transmission schedule found on Wolfgang Herrschaft (DAHLIE) in 1961 [5]. Click for a close-up.

 Original transmission schedule


Inbound traffic
The agent would listen to messages from the Centre (German: Zentrale) each morning at 08:05 or evening at 20:05 at one of the frequencies listed in the bottom right corner of the schedule above (6.500-6.750 MHz). Messages addressed to the agent were preceeded by his station number: 32.

Transmission schedule of the Centre (translated)

The messages from the Centre were transmitted either in morse code or as spoken words by a French Numbers Station. They were usually encrypted with a one-time pad (OTP) that was unique for each agent. Once the agent had taken down the message, it was deciphered with the OTP and then converted from numbers to letters, using a predetermined scheme. The corresponding page of the OTP was used only once and was destroyed immediately after use.

Outbound traffic
If the agent wanted to send a message to the Centre, he picked the two-letter combination from the schedule for the given day in the given month. For example: for the 31st of July, he gets the combination '
h G
'
. The two letters are used as an index into the two columns at the far right of the schedule: ZEIT (time) and FREQUENZ (frequency). The lowercase letter '
h
'
yields the time for the transmission: 15:57, whilst the uppercase letter '
G
'
defines the frequency: 5.414 MHz. In the transmission, the agent would identify himself with his station number: 32.

The message itself consisted of numbers only. In most cases the text was first converted from letters to numbers using a fixed scheme, and then encrypted by means of a one-time pad (OTP). At the Centre, a copy of the OTP was used to decipher the message. The corresponding page of the OTP was used only once and was destroyed immediately after use.




Circuit Diagram
The EE-2 transmitter is basically a single-penthode Miller oscillator, built around an American 6AQ5 tube with a crystal – resonating in parallel mode – connected between the g1 and ground. At least two versions of the transmitter circuit exist, as the one in our collection differs from the one shown in Chapter 80 of Louis Meulstee's book Wireless for the Warrior, Volume, Supplement [1]. Below is the circuit diagram of the transmitter in our collection, which we have named Mark I.

French plug-in transmitter EE-2 Mark I

We assume this design to be first one. Apparently there were some issues with the stability of the circuit, as the version shown in the forementioned book [1] has two additional RFCs (L3, L4), one additional capacitor (C5), and one additional inductor (L5) in series with coupling capacitor C2. The additional components are shown below in red. We have named this version Mark II.

French plug-in transmitter EE-2 Mark II






Bottom view of the French plug-in Transmiter Type 2 Mark I

Interior
The transmitter is very service friendly. The interior can be accessed simply by holding the two knobs at the front panel and sliding off the case shell towards the rear. This reveals the interior as shown in the image above. The only active part is the 6AQ5 valve, which can be swapped in seconds should this be necessary. All other parts are passive (resistors, capacitors and coils).

The device featured here, was found with a General Electric 6AQ5 valve with a production date of 2-52 (week 2 of 1952). It is likely that this is the original valve that was issued with the device.

Restoration
The device was found in the state that is visible above and in the images below. After dusting off the front panel, the interior was thoroughly inspected for faillures. When no issues were found, a 7.015 MHz crystal was fitted, along with a suitable antenna and counterpoise, after which a 6.3V/250V power source was connected. It worked straight away and after tuning the front panel controls, it produced a nice and stable morse tone when operating an external morse key.

As no morse key or morse slide pad was found with the device, we decided to test it with the slide pad of the earlier BCRA transmitter, which is very similar. For this purpose, a yellow/blue cable was made to connect the slide pad to the yellow and blue sockets of the EE-2 transmitter.

As the power cable for connection to the socket of an EL84 valve was also missing, we decided to create a functional reproduction cable with red, green and black banana plugs to connect it to the red, green and black sockets of the device, using a modified valve extender 1 as a plug.
  
Power cable and cable for connection to external power supply

It is important to note that regular banana plugs cannot be used, as the five sockets at the right side of the device are spaced too close. It is necessary to find regular 4 mm banana plugs with a narrow grip, such as the ones shown in the images. Such plugs are also visible in the Stasi file [5]. To allow the transmitter to be connected to a regular power supply unit – for demonstration and test purposes – an extra cable with a noval socket and three banana plugs was added as well.

  1. A valve extender, or Noval Socket Saver, is used by HiFi enthusiasts for saving the existing noval sockets of an audio amplifier. It is placed between the valve and the existing socket.  Example

Transmitter outside its case shell
Interior - top view
Interior bottom view
Tank coil with switch-selectable taps
6AQ5 valve
Top side, seen from the front left
Top side, seen from the front right
Top side, seen from the rear right
Top side, seen from the rear left
Bottom side, seem from the rear right
 Bottom side, seem from the rear left
 Bottom side, seem from the front left
 Bottom side, seem from the front right
C
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C
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Transmitter outside its case shell
C
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Interior - top view
C
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Interior bottom view
C
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Tank coil with switch-selectable taps
C
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6AQ5 valve
C
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C
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C
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C
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Top side, seen from the front left
C
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Top side, seen from the front right
C
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Top side, seen from the rear right
C
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Top side, seen from the rear left
C
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Bottom side, seem from the rear right
C
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 Bottom side, seem from the rear left
C
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 Bottom side, seem from the front left
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 Bottom side, seem from the front right

Connections
Transmitter
At the right side of the transmitter are five sockets for connection of the power supply and the morse key. These sockets accept regular 4 mm banana plugs, but only with a narrow insulation cap, as the space between the sockets is insufficient for regular caps. To avoid mistakes, the sockets are coded with coloured dots on the top surface of the transmitter, as follows:

  • Red
    +240V
  • Green
    6.3V
  • Black
    0V (GND)
  • Yellow
    Key
  • Blue
    Key (GND)
6AQ5
6AQ5 is an American valve (tube) that was originally intended for application as a 12W audio frequency (AF) amplifier and later also in the vertical deflection of a television set. In the French transmitter however, it is used as an oscillator/PA for the 4 to 10 MHz range.

 6AQ5 datasheet

Click to see more

EL84 socket
Below is the pinout of the EL84 valve. This valve is not present in the transmitter but in the broadcast receiver that was used as a power supply. It was commonly used in the output stage of the receiver's AF amplifier. It requires a 9-pin B9A Noval socket. The layout is as seen from the bottom of the valve (i.e. the solder side of the noval socket in the receiver).

  1. not connected
  2. not connected
    g1
  3. not connected
    k, g3
  4. 0V (black)
    f
  5. 6.3V (green)
    f'
  6. not connected
  7. not connected
    a
  8. not connected
  9. +250V (red)
    g2
    Pinout as seen from the bottom of the valve (i.e. the solder side of the valve socket)
P-type socket
Below is the layout of the power cable that was found with the transmitter freatured here in December 2022. It consists of a socket and plug, and is installed between the valve and the socket. It is currently unknown for what type of valve and/or receiver it was intended. The layout is as seen from the bottom of the valve (i.e. the solder side of the socket in the receiver).

  1. not connected
  2. 0V (black)
  3. 6.3V (green)
  4. not connected
  5. not connected
  6. not connected
  7. +250V (red)
  8. not connected
    Pinout as seen from the bottom of the valve (i.e. the solder side of the valve socket)
Specifications
  • Device
    Plug-in transmitter
  • Country
    France
  • Manufacturer
    unknown
  • Customer
    DRS-SR (French intelligence in Berlin)
  • Purpose
    Agent communication
  • Era
    Cold War
  • Years
    1954-1957
  • Frequency
    4-10 MHz
  • Modulation
    CW
  • Valve
    6AQ5
  • Power
    6.3V, +250V, Ground 1
  • Cable
    Wired for EL84 valve in domestic receiver
  • Dimensions
    223 × 103 × 34 mm
  • Weight
    530 g 2
  1. Taken from AF socket of contemporary receiver.
  2. Mark I version.
Crystals
The transmitter was usually supplied with a set of 15 crystals. Depending on the current transmission schedule, the agent would install one of these crystals. The following crystals were confiscated by the Stasi of the former DDR [5]:

  1. 4.182 MHz
  2. 4.392 MHz
  3. 4.802 MHz
  4. 5.070 MHz
  5. 5.228 MHz
  1. 5.328 MHz
  2. 5.454 MHz
  3. 5.533 MHz
  4. 5.742 MHz
  5. 5.912 MHz
  1. 6.129 MHz
  2. 6.312 MHz
  3. 6.408 MHz
  4. 6.505 MHz
  5. 6.924 MHz
Surviving EE-2 transmitters
  • Mark I
    Crypto Museum, Netherlands 1
  • Mark II
    DHM, Germany 2
  • Mark II
    Private collector, France
  1. Previously held in the collection of Edmond Codechèvre (France).
  2. Formerly held in the Traditionskabinett of the Stasi (MfS).

References
  1. Louis Meulstee, Plug-in transmitter French (2)
    Wireless for the Warrior, Volume 4, Clandestine Radio, Supplement.
    September 2015. Chapter 80.

  2. Detlev Vreisleben, Information about French Plug-in Transmitter Type 2
    December 2022.

  3. Notes in former MfS Traditionskabinett (internal museum)
    Photograph kindly provided by Detlev Vreisleben [2].

  4. Bundesbeauftragte für die Stasi-Unterlagen (BStU) 1
    Federal Commissioner for the Stasi-Records.

  5. MfS II/3, Merkblatt GM 'Fallstein'
    Description of confiscated French plug-in transmitter and burst encoder.
    BStU, MfS-HA II, Nr. 41276. Berlin, 8 September 1961. 2

  6. MfS, ... vom französischen Geheimdienst an Spione in der DDR übergebene Funkgeräte
    Equipment handed out by French intelligence to spies in the DDR (German).
    BStU, MfS. VVS JHS oOC1 - 70/88, page 163. 2

  7. Paul Maddrell, Exploiting and Securing the Open Border in Berlin:
    the Western Secret Services, the Stasi and the Second Berlin Crisis, 1958-1961.
    Woodrow Wilson International Center for Scholars. February 2009. Page 19.

  8. Philip Parker, The Cold War Spy Pocket Manual
    ISBN 978-1-910860-02-1. UK, 8 October 2015. pp. 139-140.

  9. MfS II, Photographs of confiscated Western equipment 2
    BStU, MfS-HA II, Nr. 41369. Undated.
  1. Full name: Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes der ehemaligen Deutschen Demokratischen Republik (DDR) — Federal Commissioner for the Records of the State Security Service of the former German Democratic Republic (GDR) — officially abbreviated BStU.
  2. Document from BStU archives [4], kindly provided by Detlev Vreisleben [2].

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