Some of the US&S guns may have been in railroad service, most were marked for the railroad that issued them. Sometimes the RR mark is under the rubber butt cover over the end of the pistol grip. Pull off the rubber protector and look, rifles and shotguns too. I've seen one pistol, rifle and shotgun all marked "GNRR" under the rubber butt protectors. I saw another gun marked at that location "B&O RY Special Agent" and the badge number it was issued to. Similar guns issued to Railway Express and Railway Post Office. Happy hunting. Oh, by the way, the guns of other makers were also used in rail service, not just US&S.