The choke and bore next to each other, followed by "CHOKE" was used until c. 1910 Jerry. The gun is probably therefore pre-WWI and I suspect the gun was re-proved prior to 1921, after the right barrel was slightly honed and choke opened.
Cornell Pubs also has a 1908 ML catalog reprint and the gun should be illustrated
https://www.cornellpubs.com/old-guns...hp?item_id=469