The 12ga was the slug gun, with rifled barrels. He posted about the guns a number of times on this forum. John died several years ago. A search of his posts under the 'user list' area at the top of this page might get you to the posts which might answer your questions about the guns...Geo

p.s.: did you find the date code?
p.p.s.: Doug Mann who posts here sometimes is a cousin of John's and may know more specifics.