This is a Civil War era Whitney Percussion Revolver with US military inspector markings. Its a Second Model 3rd type with the Colt style loading lever latch. Serial number is in the 17,900 range with all matching numbers (see photos). US inspector initials are all over this gun and can be found on almost ever major component. If you look very closely at the left grip, there is a small fragment of the original inspector's cartouche remaining and located about half-way between the grip screw and the bottomstrap.
Overall condition grades to NRA Antique Good with smooth grey metal that has good markings with wear to the edges. This gun was probably used by a Union Cavalry regiment...just look at all the holster wear to the muzzle and front sight. Interestingly enough, its serial number is in the 17,900 range and is right in the middle of several serial numbers known to have been issued to the 19th Pennsylvania Volunteer Cavalry during the Civil War. The grips are solid and in good shape with no breaks and good wood to metal fit. Both grips are serial numbered to the gun with inspectors initials inside. Good working action and Very Good+ bore. A good example of an uncommon Martially-marked Civil War revolver.