...and thanks all for the OT discussion on Simmons vent ribs on M12/42s. I appreciate the education. I now understand that my Heavy Duck is likely a "Simmons Marketed" gun due to the presence of the proofmarks.

I also noticed that the rib on my gun says PATENTED. I looked it up and E.P. Simmons applied for a patent in 1948 to cover his vent rib design. It was awarded in late 1952 (US2620583). Could be licensing negotiations took another two years before Winchester could start doing it themselves, and might explain Simmons being allowed to "re-strike" the Win proof. Interesting that the patent diagrams for the rib show essentially a M12 with a "poly" choke system.

Bryan