M-209 / Hagelin C-38
Designed by Boris Hagelin, the M-209 was a compact, portable mechanical cipher device
used extensively by US front-line troops in WWII. It features 6 pin-wheels with different
numbers of pins (17, 19, 21, 23, 25, 26 = 101,405,850 key combinations). The active pins
engage bars on a lug cage (drum) that performs the actual encryption as a variable Caesar shift.
Over 140,000 M-209 units were manufactured. The device weighed only 6 lbs
and could be operated by a single soldier in the field. Though the Germans (Buggisch, Fried)
could break individual messages by 1943, the tactical nature of its traffic made this less
damaging — by the time a message was decrypted, its contents were often obsolete.
The M-209 served through the Korean War until being replaced by electronic devices.