The London marks on the flats are 1887-1896, and are both provisional and definitive. Not nitro. No "choke" markings. Seems odd. Are both barrels cylinder?
The "12 C" in a rhombus/diamond, from johnmwmd's post, is a Russian full choke mark, that is if it was stamped either in Tula(Tule) or Izhevsk and maybe between the 1914 Conference & 1920 when the State assumed control. Interesting thread and I wish I had been following it.
For now I agree with 400 NE that the post by revdocdrew and Jeff G. could be from the Paris proofhouse, but a close-up pic of all the marks would be beneficial. The "E(backwards)P" is a post 1897 voluntary, standard, in the white, joined tube proof at 14.2k psi, otherwise it would have "N.A"(non assemble).
As a side note, France empowered the Paris commerce body to establish a proof facility in late 1895. Prior to that a stamp of "A crossed palms F" in an oval noted a gun made in France but not in St. Etienne. Boutet & Bernard had their own stamps but I don't think "E(backwards)P" was one of them.
Kind Regards,
Raimey
rse
