This rare M4 Enigma cipher machine, discovered aboard U-85 inside its original case and with a radio headset, was used to encode German military messages. “As German subs were operating off America’s coast, we didn’t know what they were saying in their communications,” David Bennett, curator of maritime history at the North Carolina Maritime Museums system, said.
The British had cracked Enigma 3, but, as Bennett points out, “[r]ight at the beginning of 1942, the German navy switched over from Enigma M3, which had three rotors, to Enigma M4, which had four rotors. The code became so much more complicated to break .… The Allies could no longer read the German naval codes, and it’d be some time before they’d crack the Enigma again.”