I think Buckaroo Lou is right. I want to say HR is for Lew Horton and stands for "Horton Rodeo" but I am not sure. The gun in question has been discussed here before. It has been for sale for a long time, at least several months. I believe the general consensus was that the nickel is probably not original. An original USFA nickel should be virtually seamless and this gun shows clear seams where the trigger guard and backstrap meet the frame.