I have a very late 12 gauge H grade with 28" twist bbls, SN on frame is 73,338 & on barrels 73,342 I have never actually measured the wall thickness but with a total weight of 6 lbs they are rather thin. While I have never seen it SN 73,337 is listed as a 12 ga with 28" Damascus barrels. Damascus there may, or may not, mean Twist, some folks just do not differentiate between them. I have never shot this gun but a few times with some very light loads as I feel the barrels are a bit suspect.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra