WHAT IS IT?

I believe this is an antique coin holder for an old Post Office Dept. cash drawer, or USPS cash drawer. I think so because 1: My Dad and I are both retired from the Post Office (he is deceased), and 2: in 1975 my youngest brother went 3 for 3 with 3 home runs in his last Little League game. A carrier friend of my Dad's who worked there at the time wanted to do something special for him, and as I remember it, he took an old coin holder like this that he got from the P.O., cut off 1 of the half moons, and made a presentation holder for the 3 baseballs with it. I'm SURE this happened, BUT, it is not marked "Property of P.O. Dept" or "USPS" anywhere, so I can't stake my life on it. Maybe all pieces of P.O. preoperty like this WEREN'T marked as such. I would appreciate ANY help in verifying that this is indeed an old Post Office cash drawer coin holder, or just WHAT it is! Thanks in advance!