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) |
