I have a early 1 million serial numbered Koshikowa ( sorry Grammer) with what looks like somone went a little crazy with a concentric circle stamp on the mum 2 strikes. it also is a school rifle with double school stamps. It also bares the two 00 serial 3 prefix.
Would you say this is a defaced mum or a removed from service stamp over the mum? I may be think the stamp guy was having a bad day when this was stamping it as out of service.