The barrels were cast by LaPan's Foundry in Hudson Falls, New York. My catalogs do not list a barrel with the dimensions shown. Maybe they were limited edition pieces. LaPan made very good quality barrels but quit selling to the public several years ago.
Correction: The barrels appear to be LaPan's pattern number 6-A which is listed as a French or English 1-pounder. Sold for $375 back in the 70's.