The Russian flasks are round,and flat, with a added metal spout. The body is often banded around the center seam with metal, and often has rings for a shoulder strap. On a couple I have seen, the plug is metal with a measure that fits into the neck of the spout, which sometimes is attached to the metal band.
If you Google Ft. Ross, you will find quite a lot of information on the Russian fur trade. I think they were in California for about forty years.
Hungry Horse