Well, I'm to blame too...Never looked at the face of the action on my Reilly 16bore 27853 (dated 1886). Scott gas check patent is there...use nr. 1953:

Which means its twin 12 bore 27854 probably has the next stamp up or near to it:
27853 - E.M. Reilly & Co., Oxford Street, London & Paris Improved Patent. 16 bore, Shotgun SxS. Dolls Head; Side-clips; S-L,
Scott climax action Pat 761 use #2112, Perks, crystal indicators, Scott gas check 617 use #1953, Whitworth Steel barrels, 1st of pair. Argo44s gun .
"Not for Ball"27854 - E.M. Reilly & Co., Oxford Street, London & Paris Improved Patent. 12 bore, Shotgun SxS. Dolls Head; Side-clips; S-L,
Scott climax action, Perks, crystal indicators, Whitworth steel barrels, 2nd of pair. (Buffum)
I also see the Scott "climax action" pat 761 with a use number 2112.

Where might the patent use numbers for crystal indicators be found? Behind the plates?