Mike D - The limited pictures fail to provide enough detail for me to authenticate the engraving on the scope tube as legitimate. I intend to send an email to the seller requesting a better close up picture of that area. If I get a response I'll post my opinion.
As to the Serial # 1356 that Jim G mentioned; I have one record of the 330 scope serilized lower than that (Serial # 1155). That scope had X-Hairs. My record on #1155 has no info concerning its rings or ring screws. I'll have to check my A4 and M73B1 Scope to see what the ring screws look like.
It is indeed an interesting piece which requires investigation!!
Mike Haas