The M-125, codename ФИАЛКА (Fialka, meaning Violet) was first introduced in 1956 in the USSR, and was succeeded by the more complex M-125-3M in 1965. It was the favored machine of the Warsaw Pact and allied nations, including Cuba, and the design of the machine was based upon the German Enigma — leading it to often be referred to as the "Russian Enigma." Where the Enigma had a panel where the encoded letters would light up, the Fialka printed the message directly onto a strip of paper. Having learned from the flaws in the German design, the Russians made a number of improvements to the machines, including: Using 10 wheels instead of only 3 or 4; introducing more frequent wheel turn-overs; allowing a letter to be encoded onto itself (the great flaw of the German Enigma); replacement of the Steckerbrett with a punched card; the movement of adjacent wheels in opposite directions; and the ability to change the wiring of the wheels while in the field.
Most machines had the capability of using Latin or Cyrillic writing, and each country in the Warsaw Pact had its own customized version, with a different keyboard and print head designed for each country, as well as different wiring for the coding wheels.