The HC-520 Cryptomatic , another Crypto AG machine, can be thought of as a modern, electronic version of the CD-57. It features an LCD display with keyboard plus an external power supply for a rechargeable NiCd battery pack. Alternately,  6 to 7.5 VDC volts at 0.5 amps external power can be applied via the 'D' socket at the rear.  To encrypt messages, the user would enter the plaintext via the keyboard, then read the encrypted text in the LCD display. The buffer in the machine will hold around 690 characters.
 
 

There were two identical versions it seems:

a) Military version, at times in an olive (Army colour) canvas or black cover with zipper

b) Civil version, light beige, with a black cover.

Two double-sided cardboard cards were originally supplied and contain flow-charts for enciphering and deciphering, in English and French.

This model is the smallest in the HC-5xx family and is compatible with the:

HC-530 -  In Samsoite attaché case with printer;
HC-550 - Teletype model
HC-570 - Big - but considered to be "transportable".

Crypto AG manufactured this range until 1979 and maybe 700 HC-520’s were made ­ costing about CHF/Swiss Francs5000 each at the time.

Photos and copy courtesy John Alexander, G7GCK Leicester, England. E-mail: See Museum Info section.

Sept 20,/02