Marty: we could confirm the 1896-1904 date of proof with a close up of the barrel flats. It should be marked '1 1/4 oz
Max'.
1904-1925 would be '1 1/4 oz
Shot'.
Under the 1896 Rules of Proof 12g 2 1/2” and 2 5/8” chambers (bore .710-.740) were proved for a maximum service load
of 3 1/4 Dram Eq. with 1 1/4 oz. shot. (1220 fps)
Under the 1904 Revisions, Supplementary Nitro Proof for 12g 2 1/2” and 2 5/8” chambers was for a service load 1 1/8 oz.
'70' (without mm) would be a post 1989 chamber length mark, but if reproved after honing it should have a Crown over R and be marked with bore in mm and BAR, and will have a Proof House date code
Bore 10” from Breech L. .787 choke.030 R .734 choke .010
That is .737" on L?
Cornell Pubs has 1900, 03', 04' & 06' Greener catalog repros so if we can narrow down the DOM you could order the appropriate catalog to ID the grade
https://cornellpubs.com/product-tag/w/page/4/
Threaded Mode