Typically If I see something like that "38" stamped on a set of rifle barrels, my first thought is
*thirty-eight bore, small for a .500 rifle, just the right size before final reaming and rifling...*
...but those muzzles don't look to have an obvious ring seam like you'd see on a re-line job.

Hm.

Gotta do some proof-mark homework.
One of our forum members here, (400NitroExpress) is a proof-mark encyclopedia on two feet.
Perhaps we need to get him on this one.

Are there any other proof marks, anywhere else on the metal?




Cheers
Tinker