According to the source I found, the 29 Corn St. address would place it between 1858 and 1888. After 1888 it changed to 39 Corn Street.

http://researchpressuk.wordpress.com/2010/02/16/george-gibbs-bristol/

Proof laws are strict and explicit, and I feel sure that re-lining the barrel would have required re-proofing, but I may be wrong about that. That could explain the 1952 proofs, but Chuck Hawks says that the .22 Win Mag as introduced in 1959. Maybe it was a different .22 caliber first?

Curious.