CD-57 by Crypto AG

The CD-57 was a mechanical, handheld device derived from the CD-55 and was produced in 1956 and 1957 by the Crypto AG company.

The CD55 and CD-57 devices look identical from the exterior but the difference is very simple - it lies with  the keying mechanism.
The CD-55 works in the same way as the C-38, M-209 and C-446, and features simple stepping (so that could be broken easily by the NSA at the time). The CD-57 has a much more advance keying mechanism, based on the same principle as the C-52 and CX-52 (which was VERY difficult to break).

Development of both machines was started in 1955 and was completed in 1957. Both machines appeared on the marked in 1957. The differences were never explained to potential customers. NATO and NATO-friendly countries were allowed to buy the CD-57. Other countries (in particular the Arab countries) were only offered the CD-55.

A variant, namely the CD-57 (RT), is the same device but it lacks rotors. Instead, it uses a reader for a one time tape. CD-57's were essentially unbreakable provided their  one-time, tape system was properly handled and secured. The French, in particular, liked these CD-57's. Weight: 2 pounds.

The CD-57 with cover open (top) and cover closed (bottom). (Photo courtesy John Alexander, G7GCK) 

The CD-57 (RT) front view - bottom. (Photo courtesy John Alexander, G7GCK) 

The CD-57 (RT) front view - top. (Photo courtesy John Alexander, G7GCK) 
Top view. (E-bay photo)
Closeup of cipher wheels and character counter .The NATO version of the CD-57 was designated C-1-0.  The ciphers obtained with this machine are of the double substitution type and mechanically produced (E-bay photo)

CD-57 rotor #29 showing contact detail. (Photo via E-bay)
Credits and References:

1) Paul Reuvers <paul(at)>

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Oct 14/16