I don't know that there's a lot of doubt. It would seem that the um date of manufacture would be 1875 as that is when the change in the name to Lang & Son occured. What is the address on the top rib 22 Cockspur? I think the tubes wear the "J.L." stamp, not J.C., a J. Lang being either the son-in-law of James Purdey or grandson of James Purdey. Does it have the March 8th 1870 patent #687 Lang screw-grip action? I wonder if there are worn proofmarks closer to the forend hanger?
Kind Regards,
Raimey
rse