Standard adjustable wheel set for the Cold War-era Russian M-125 cipher machine, codenamed 'Fialka,' on their rotor shaft. The ten wheels have non-matching serial numbers, but all begin with a "6K" prefix, indicating Czech wiring. The wheels would be arranged on the rotor based on a daily key, as with the Enigma. This wheel-set stems from the PROTON-2 operating procedure, introduced in 1978, which added greater complexity to the wheels—like the initial, fixed rotor set, each wheel has 30 electrical contacts on either side. These adjustable wheels additionally feature moveable letter index rings and interchangeable/rotating wiring cores, thereby increasing complexity and making encoded messages more difficult to decode.
The Fialka is an electromechanical, wheel-based code-generating and decoding machine. Its development came after World War II, and was based loosely on the German Enigma machine, with rotors moving to a new position each time a key is pressed, creating a new electrical circuit and an alphabetic substitution for the letter that was pressed. However, the Fialka incorporates a number of different features from the Enigma that made it a much more daunting cipher-generating machine. These features include the use of 10 rotors (each with 30 contacts), wheels rotating in opposite directions, and more frequent wheel stepping. In addition, the rotors could be quickly rewired in the field, and input and output from the machine was accelerated via the use of punched paper tape.
Being regularly produced starting in 1956, the Fialka quickly became a primary cipher machine for all of the Warsaw Pact countries and Cuba. Each country had the Fialka keyboard modified to their language. The Fialka was in use by Russia and its allies well into the 1990s, and very little information was available about this machine until 2005 as it had been kept secret. Few Fialka machines remain as they were systematically destroyed by the Soviet Union and its successors as the machines were taken out of service.
