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Mirror probe kit
Versatile inspection mirror

In the covert and espionage trade, small mirrors are often used to inspect areas that are difficult to reach, for example inside or behind a piece of furniture. Inspection mirrors provide a good way for looking around a corner, in the same way as a dentist does when inspecting a patient's teeth.

Inspection mirrors, or mirror probes, come in many flavours, in various sizes and diameters, but the most common one consists of a small circular mirror on a short stick. They can be used to look around a corner when repairing a piece of equipment, but can also be useful, e.g. when searching for covert listening devices (bugs).

The image on the right shows a versatile mirror probe kit with 3 different sizes of mirrors with extensible sticks and a built-in tourch light, as it was used by the State Security (MfS, Stasi) of the former DDR (East-Germany) during the Cold War.
  
Three different sizes of mirrors

The kit consists of three different mirrors with diameters of 12, 20 and 30 mm respectively, each with a built-in fitting for a miniature light bulb, that can be mounted on an extensible stick. At the other end of the stick, a blue grip with a 3V battery is fitted to power the lamp. For transit, the kit is packed in a nicely organised leather wallet, with a dedicated slot for each item. When used in combination with a borescope, it is possible to look around a corner inside an object.

Leather carrying case Sub-case with the actual mirrors Complete kit Three different sizes of mirrors Battery holder for built-in torch light Miniature light bulbs Complete inspection mirror kit Mirror with light bulb in fitting
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Leather carrying case
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Sub-case with the actual mirrors
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Complete kit
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Three different sizes of mirrors
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Battery holder for built-in torch light
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Miniature light bulbs
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Complete inspection mirror kit
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Mirror with light bulb in fitting

Complete kit
The diagram below shows the contents of the leather wallet. There are three stick segments, of which one holds the light bulb at the end. This allows the stick to be made 25, 45 or 65 cm long. Each segment has a contact wire at its core, much like a rigid coaxial cable, through which the current is passed from the battery in the blue grip to the light bulb at the mirror-end of the stick.


The light bulb is lit as long as the white button at the side of the battery holder is depressed. The lamp is powered by a 3V 2R10-size battery 1 that should be installed inside the blue grip. It is 74.6 mm long and has a diameter of 21.8 mm. Although these batteries are less common today than they were in the 1960s and 70s, they are still available from a number of brands (2018) [1].

  1. Also known as a Mallory No. 8 battery, or duplex battery.

Mirror with light bulb in fitting Mirror with light bulb Miniature light bulb screwed into the end of a segment Bottom side of a segment, showing the inner contact wire Battery adapter plug, to be inserted at the bottom of a segment Battery adapter and segment Battery adapter fitted to the battery holder (grip)
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Mirror with light bulb in fitting
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Mirror with light bulb
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Miniature light bulb screwed into the end of a segment
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Bottom side of a segment, showing the inner contact wire
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Battery adapter plug, to be inserted at the bottom of a segment
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Battery adapter and segment
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Battery adapter fitted to the battery holder (grip)

References
  1. Wikipedia, List of battery sizes
    Retrieved October 2018.
Further information
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Crypto Museum. Created: Monday 08 October 2018. Last changed: Saturday, 13 October 2018 - 10:09 CET.
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