I am researching the story of a Third Model Russian owned by my father, a longtime firearms collector. We have requested a report from S&W. This report has not yet arrived, but the piece appears to be one of the 13,000 Third Model Russians made in 1874-1878 for the commercial market. I am consulting this learned group to see if anyone knows the meaning of a marking on the right side of the barrel. It reads, "D. A. Russell, S.L.O.", nicely hand-engraved. While this marking could have been added at any time in the gun's long history, around the time of its manufacture Fort D. A. Russell (now F.E. Warren AFB near present-day Cheyenne, WY) was the largest post on the Western frontier. As for "S.L.O.", I'm completely stumped. The only use of that acronym I can find from the 1870s is San Luis Obispo, the county and city in California. An individual's initials? Sxxx Line Officer? Any thoughts or information would be appreciated.