Very nice Condition, mechanically like new. Nice barrel for an original Black powder Antique. Original less common 5.5" barrel. Nice stag horn grips. Could be an early refinish. If it was it was long ago. Stampings and numbers are very clearly defined. 

Remington Model 1875 Single Action Army (a.k.a. Improved Army or Frontier Army)[2] was a revolver by E. Remington & Sons. It was based upon the successful New Model Army (Remington Model 1858) with both revolvers having the same size, appearance, and the removable cylinder. The new 1875 Remington differed mainly from the older 1858 percussion model by having a bored through cylinder chambered for metallic cartridges. Thus, in 1875, Remington entered the cartridge revolver market with this big-frame, army style revolver, intended to compete with the Colt Peacemaker.[3] Ordinary citizens and Old West lawmen alike recognized the sturdy quality of the new Remington revolvers.[4] This design was followed by the Model 1888 and the Model 1890.