The Allies did use a number of coding machines similar to Enigma. The British Typex machine was, in fact, derived from a commercial Enigma machine. Such machines were sold to companies and corporations in the 1920s and 1930s, though they were less secure than the military version. The first models of Typex were simply just one of these commercial Enigma machines hooked up to a teleprinter to simplify the process of decoding or encoding messages. However, the British quickly improved on it, adding more security features. Later model Typex machines had more rotors than contemporary Enigma machines. Those rotors also turned more frequently than Enigma rotors, adding even more complexity. The Americans, meanwhile, had produced their own cipher machine, SIGABA. This was even more secure than Typex or Enigma. SIGABA used 15 rotors, rather than the 3-5 of Enigma or 5 of Typex. Rather than rotating its rotors sequentially, as Typex and Enigma did (this introduced a vulnerability), SIGABA rotated them in a pseudorandom manner. While Typex in theory could be broken in a similar manner to Enigma, SIGABA could not. This explains why the Allies didn't simply copy Enigma - they had their own, better versions.