Everyone knows about the Enigma cipher machine (even my neighbor knows it). But Hagelin cipher machines series C (C-35, C-36, C-38, C-446, C-48, ...) were the most used in the world from 1935 until the 1970s. Armies and embassies of almost every country have used it. The best known of these machines designed by the Swedish Boris Hagelin is the M-209. The Corona company has built more than 140 000 copies for the US Army. M-209 (named CSP-1500 by US Navy) is basically the Hagelin C-38. This machine has been used by the US Army during the 2nd World War and the Korean War. The US has equipped many other armies of the M-209, and among them, the French army.
The M-209 is a machine to encrypt or decrypt only by mechanical means. It can print the product message (the ciphertext or plain text). By comparison the Enigma machine uses electricity and its result (encrypted letter / plain letter) appears as an enlightened letter which must be copied manually.
The M-209 is small: 18x14x8 cm (5.5x3.25x7 inches) and weighs 2.7 kg (6 pounds). The Enigma is much greater: 35x28x15 cm (13.5x11x6 inches) and weighs 12 kg (26 pounds).
Many Enigma messages were read by the Allies during the 2nd World War. Similarly Armies of the Axis especially the Germans have read many messages produced by the M-209. The American cipher machine Sigaba and the German machine T-52e are much more secure, but they were reserved for the headquarters.
Well used (it is very difficult in war times), the M-209 can provide very good security. Thus, if the message size is less than 700 characters and the message key is not reused, the message can't be decrypted with the techniques used during the 2nd World War and Cold War. Even today, a message with a size of 250 characters can not be broken using computers. Conversely a 250 characters Enigma message is readable (Breaking German Wehrmacht Ciphers).