Geno,
I love the Russian guns you post. Always a learning experience for me.
I have seen that ridge work on other barrels. It was apparently rather common early on for high grade guns. I have no definite evidence of how it was done, though I could suggest several ways of doing it. Interesting that they choose to etch the barrels.
I think I found the barrel maker;
A Marneffe & JJ Dupont, Liege 1856-1863. Submitted 1524 barrels for proof in 1856. Granted a patent in 1861
JJ Dupont Liege successor to Marneffe & Dupont 1865-1870
Also found:
J Dupont & Fils 1886
J Dupont & Fils ILLIC 1888
Jean Dupont 1 Rue Haute Prealle, Herstal 1881-1885
Joseph Dupont 46 Rue de Robermont Leige 1892
I can not find any of them with a registered trade mark. Probably why he used his name on the barrels. The single name dates the gun to 1865-1870 IF the info I have is correct.
Both Jean and Joseph have several patents between them. Mainly regarding locking mechanism.
Would that engraving of the hunter with dog be a typical Russian image of that era?
Pete