CSP-1500 case, manual and open cipher.

CSP-1500 Showing M-209 style carrying case, cipher machine, small tube containing ink pads, screwdriver, tweezers, and small tube containing oil. The tubes and tools all fit inside the top cover.

Cipher with top cover open.Cipher with inner cover open.

CSP-1500 showing the top cover and inner cover opened.

DESCRIPTION OF CSP-1500 a.k.a. M-209:

The CSP-1500 (M-209 in the Army) is a portable, hand-operated, tape-printing mechanical device designed for encipherment and decipherment of tactical messages. Its cryptographic principle is that of reciprocal substitution alphabets, achieving the effect of sliding a standard alphabet sequence against a standard reversed alphabet sequence. This is achieved by means of a train of gears in which the number of active teeth on the driving member is varied in accordance with prearranged settings of the keying elements, a high degree of irregularity is effected in the shifting of each alphabet against the other.

This machine was developed as a replacement for CSP-885 (M-94) for use in tactical situations. It is derived from a machine created by B. Hagelin in Sweden during the late 1930s. In 1940 several machines were purchased by the Army Signal Corp. and after some simplification to make it easier to build and more rugged manufacture began in the United States. Its first general use was during the African invasion of Nov 1942. Over 140,000 units were produced during WW II.

M-209 was popular in the Army because it is small, light, an operator can be trained in just a few hours and special security was not needed for the machine itself. However, it was never cryptographically secure and so could only be used on low level, tactical traffic where it only needed to delay an enemy by a few hours.


The Army and Navy used the same keying and operating procedures for the CSP-1500 and the M-209.
Instruction manual for using the M-209.
A key list for the M-209.


Weight 6 pounds.
Average speed of 30 characters per minute.


The information enclosed here is excerpted from:
Plans for R and D Crypto Equipment. This is available from NARA; NSA Historical Collections 190/37/7/1, NR 3288 CBOM71 16503A 19440909.
Maintenance Instructions For Converter M-209-A. This is available from NARA; NSA Historical Collections 190/37/7/1,, NR 2300 CBLL37 15121A 19430528 (box 800 )

Photographs by Russel Booth, San Francisco, CA.

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