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Enigma Rotor Z → K → Enigma I → Zählwerk → ← C
Commercial Enigma A26
The Enigma D was developed in 1926 as the successor to the
Enigma C.
The official model number was A26 and it was given the internal
designator Ch. 8 by the manufacturer Chiffriermaschinen AG.
It was replaced a year later by the nearly identical
Enigma K (A27).
The Enigma D contained many improvements over the Enigma C. First of all,
the top lid of the machine was made more accessible, so that it was
easier to alter the basic settings (key).
The three coding wheels were now mounted on a
removable spindle,
so that the order of the wheels could be changed as well.
Furthermore, the reflector (UKW) became settable,
which means that it could be set to any of 26 positions.
All this increased the maximum number of permutations.
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As a result, 4 wheels protrude the top lid
and hence there are 4 windows through which the current settings can be viewed.
Because of this, it is sometimes assumed that this is a 4-wheel Enigma
machine. Although stricktly speaking there are 4 wheels,
the leftmost one is the UKW.
It should therefore be defined as a 3-wheel machine with a
settable UKW.
The machine was built on an improved die-cast chassis and the order of
the keys and the lamps was now similar to that
of a standard German typewriter (QWERTZ... rather than ABC...).
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Looking at the Enigma Family Tree it is obvious that around 1926
the Enigma D was the core product of the manufacturer, Chiffriermaschinen AG.
All further Enigma machines would be based (largely or in part) on the Enigma D design. The Enigma D itself was short lived and was replaced approximately
a year after its introduction by the nearly identical Enigma K.
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The images above were taken from the Commercial Enigma machine with serial
number A818 in our collection. This machine was found in 2011 in near mint
condition and still had its original — commercial — wiring [1].
Research has shown that it was produced or sold in 1927 [2].
It is therefore difficult to determine whether it is an Enigma D (A26)
or Enigma K (A27).
Apart from minor production differences, these machines are identical.
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The Enigma D was a machine with 3 coding wheels
and a settable reflector (UKW).
All 4 wheels protrude the top lid of the machine.
As the UKW has a thumbwheel for setting its position, it is nearly identical
to an ordinary coding wheel. As a result, the machine is sometime erroneously
thought the be a 4-wheel Enigma. The UKW does not move during encipherment.
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The wheels are made from steel and aluminium,
and have a Bakelite inner core that holds the 26 contacts at either side.
Each wheel can be set to one of 26 positions, each of which is identified
with a letter of the (Latin) alphabet (A-Z).
The image on the right shows a close-up of wheel number III.
As you can see, the aluminium thumbwheel is
nicely polished
and has rounded edges. This was common for commercial Enigma machines
in those days.
Later machines, such as the military Enigma I
were less shiny and were less well finished.
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More details of the wheels (including the ETW and the UKW) in the
images below.
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The wheels of Enigma A818 (see above) contain the standard commercial
wiring as presented in the table below [1]. This wiring was identical
for all commercial machines, including the later Enigma K (A27).
Although the wiring of the wheels was changed by some customers,
they often left the wiring of the UKW intact. As far as we know, the
wiring of the ETW was never changed.
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Wheel
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ABCDEFGHIJKLMNOPQRSTUVWXYZ
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Notch
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Turnover
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#
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ETW
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QWERTZUIOASDFGHJKPYXCVBNML
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I
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LPGSZMHAEOQKVXRFYBUTNICJDW
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G
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Y
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1
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II
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SLVGBTFXJQOHEWIRZYAMKPCNDU
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M
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E
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1
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III
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CJGDPSHKTURAWZXFMYNQOBVLIE
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V
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N
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1
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UKW
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IMETCGFRAYSQBZXWLHKDVUPOJN
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Operating instruction for the Enigma are very difficult to find.
This is partly caused by the fact that the machine is extremely
easy to operate, whilst most users (e.g. the German Army) developed
their own operating procedures. In many cases the instructions where no more
that a few typed A4 pages, such as with the
Enigma A28 Zählwerksmaschine
(see: download).
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For the common commercial machines, however, a small 20-page booklet
with a clear description and simple operating instructions was released.
It was also used as a brochure.
The image on the right shows such a booklet. The first page shows a
picture of a commercial Enigma machine, plus the name and address
of the manufacturer
Chiffriermaschinen AG in Berlin.
The book in the images is aged somewhat by moist after all these years,
but is otherwise in excellent condition. Instruction booklets like this one
are an extremely rare find.
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The front cover of the booklet
shows the serial number of the machine
that it was issued with, written with a red pencil, in the top right.
In this case, it exhibits serial number A833,
which is in the same range as the Enigma machine (A818) shown above.
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Descendants of the Enigma D
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In 1927, one year after the introduction of the Enigma D, several developments
of improved machines were started. This lead to a range of new - improved - commercial
machines and advanced high-end machines. The later military machines
were also initially based on the Enigma D.
The following machines are directly developed from, or inspired by, the Enigma D:
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- Reichswehr D (Ch. 11a)
Machine with a single-ended Steckerbrett. This ultimately lead to the
developement of the later Enigma I (Ch.11f) used by the Reichswehr
(later: Wehrmacht).
- Enigma K (A27, Ch. 11b)
From 1927 onwards (right up to 1944), this was the main non-Stecker
machine. Many improvements were made and many different versions exist.
It was, for example, the basis for the Enigma T (Tirpitz),
the Swiss K variant
and the Enigma KD.
- Zählwerk Enigma (A28, Ch. 15)
This was a range of high-end Enigma machines with advanced mechanics
and enhanced cipher security, such as multiple wheel-turnovers.
The later Enigma G range (G31) was also based on this machine.
- Enigma Z (Z30, Ch. 16)
This was a numbers-only version of the Enigma machine. It had just 10 keys
(0-9), 10 lamps and the wheels each had 10 contact points.
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- Paul Reuvers and Marc Simons, Wiring of Enigma A818
Wiring of the A818 verified in October 2011 as commercial wiring.
- Frode Weierud, Enigma serial number research
Forthcoming publication.
- Chiffriermaschinen AG, Enigma booklet
Instruction booklet with images.
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© Crypto Museum. Created: Monday 14 September 2009. Last changed: Monday, 14 September 2020 - 17:06 CET.
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