The R & S may be Rogers & Son, patent holders of #397. The respective names being John Thomas Rogers & John Rogers who I assume were father and son.
Interesting thought. Are there any other patents issued to a firm that has "Son" in the name? Or any APUNs that have "Son" abbreviated by the letter S?
Cheers,
Raimey
rse
I seem to recall a Purdey (Patent) hammer gun marked as "JP&S Patent"along with patent & use numbers ?. Its a long time since I had the gun so maybe my memory has it wrong

A bit more digging confirms the Rogers as father and son, thus the R & S. Just by chance came across J D & S marking for John Dickson & Son so there are a few out there