Gday plamp,
A picture of the weapon would be of great help. Would confirm whether the piece is a 1st model Russian or later.
Charles Pates book Smith & Wesson American model is also a great reference source. The majority of the early Russian 1st models had 8 inch barrels, later issues did have 6 inch barrels.
These were for the civilian market and were not part of the Russian contract guns. A picture of the gun side on, and the writing on the barrel rib would be of great assistance. Some guns of 8 inch barrel length were lopped, in which case the barrel rib markings would not be centralised. As to serial number it could be a civilian 1st model with lopped barrel.