Thanks for the info Terry.
I got the gun today with a Stan Baker bore gauge both barrels measure a consistant .735 the right is choked to .729 and the left .694. I don't have access to wall thickness gauge I took some measuresments with a dial caliper it's about .065 in front of the chamber and about .035 just behind the choke. The bores are like glass.

With the 18.7 proof and .735 bore diameter would it be fair to say the gun was still in proof ?