Shell length for a Meteor sxs 12 ga.?

[west250]

Hi All, I have come into possession of a Meteor sxs 12 ga. that doesn't have a recommended shell size stamped on it. There doesn't seem to be a shoulder inside or anything. Any idea what length of shell I should use with it?

 

[ben hunchak]

Does it have any proof marks with a 65 or 70 in it? Maybe on the water table? I'd bet that it is 2 3/4" only as those were out before 3" got popular.

 

[west250]

I'll have a look thanks. Never thought of metric! Anything else anyone can tell me about these?