This is one of four rotors related to an ENIGMA encryption/decryption device, but does not match the serial number of B197.81 nor B198.81. No sign of a stamp of approval (inspection) marked is visible on this object. One notch on the inner Bakelite wheel is broken.
Per Ralph Simpson of the Cipher History Museum, "The ''M' was used by the German Navy, whereas A' indicates use by the German Army and Air Force." [2016-05-09].
