Manufacturing inspection stamp (stamp of approval)
Roman numeral 5, near pins
overall: 1 1/4 in x 4 in x 4 in
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. However, it does match the serial number on rotor 102616400 which suggests they were made for the same machine. Stamp of approval (inspection) marked with a Nazi swastika.
Per Ralph Simpson of the Cipher History Museum, "The 'A' indicates use by the German Army and Air Force (Navy used 'M' for marine)." [2016-05-09].