I'm looking for an original WWII caseback with Ordnance or Bureau of Ships markings for my Elgin grade 554 watch (see attachment). When I bought the watch it had a Type A-11 caseback with the following markings: US Army, Type A11, Spec No. 94-27834-B. Ser No. AF45-17846, MFR's Parts No. 2114 ORD No. W37-036ac-6600, ELGIN
which is (to my knowledge) an incorrect caseback for this watch. So, I'm looking for a correct caseback with the markings: 'ORD. DEPT. U.S.A. OFxxxxxx' or 'USN BUSHIPS' which will fit this particular watch.
Can anyone help?