Here's another Reilly SN 17364 from 1872, five years before this gun, with "J.P. Patent 1037"....advertised by Holt's:
https://auctions.holtsauctioneers.com/asp/fullCatalogue.asp?salelot=A0919+++1808+&refno=++143166E.M. REILLY & CO.
A 12-BORE PUSH-FORWARD UNDERLEVER HAMMERGUN, serial no. 17534,
29 3/4in. nitro reproved fine damascus barrels, wide rib engraved 'E.M. REILLY & CO. NEW OXFORD STREET. LONDON.', 2 3/4in. chambers, bored approx. true cyl. and 1/2 choke, push-forward underlever, carved percussion fences, action flats marked 'PATENT ACTION' and '
J.P. PATENT 1037' (likely referring to J. Purdey patent double bite, patent no. 1104 of 2nd May 1863), rounded bar, rebounding sidelocks with engraved faceted hammers, fine acanthus scroll engraving with feathered bordering, 14 1/2in. highly-figured stock (crack to left underhorn and at head to rear of right lockplate) including horn buttplate, weight 7lb. 4oz.
Holt's seemed to think the Patent use number number was for Purdey Patent 1104. However, I'm wondering if it in fact were for that snap-action under-lever. (Unfortunately no picture of the stamp.) That might make sense since Patent 1104 should have expired before SN 21369 (the gun in question) were made. (I tried to compile a chart of all Reilly guns which had a Purdey patent 1104 use number to check to see if it was consistent. It rapidly fell apart, but perhaps this was because I was mixing 1104 use numbers with that snap action patent.)
