Can anyone point me towards a guide to proof marks on London-proofed gauge or bore rifles? I'm confused by the marks on a steel barreled 20 gauge that's proofed on the barrels and not the flats with London proofs.

Between the viewing proof and the definitive proof, there's a "39" marked on the barrel. No other markings for gauge or caliber.

Any resources you can share or an interpretation?

Thanks,
CJF

http://www.shotguns.se/html/uk.html

http://www.shotguns.se/html/london_marks_in_context.html

https://www.vintageguns.co.uk/articles/514-2/

Pictures sure would help

Mike

Thank you Mike. Layout is exactly like first period (thru 1868), but I wasn't aware that Jones under-lever was that old, but I just saw it goes back to 1859, so it is feasible.