"Variations on a Theme" is the newest display to the rotating Cryptologic Treasures exhibit at the National Cryptologic Museum. The artifacts show several different, and sometimes odd, modifications made to a small World War II cipher device. None of the modifications were ever adopted.
The original M-209, though not 100% secure, protected tactical-level communications reasonably well during WWII and the Korean War.
The most elaborate and complicated modifications made to the M-209 made the machine heavy and awkward.
Both of these machines, the Navy's CSP-1500 (left) and the Army's M-209 (right) had similar modifications made to them.
Two minor modifications were made to the M-209/CSP-1500 cipher devices.
The keyboard on this M-209 is for show. The keys are simply glued to the solid wooden base.