This is an exceptional and rare U.S. Contract, Colt Single Action Cavalry Model Revolver that was manufactured in 1873. This revolver was inspected by Ordnance Sub-Inspector Orville W. Ainsworth and is stamped with his distinctive small “A” sub-inspection mark on the underside of the barrel, the trigger guard, back strap, cylinder, and left stock heel. Ainsworth’s script initials “OWA” are stamped in a rectangle on the lower left side of the grip. The revolver is boldly stamped with the unit marking: “CO.K.4.CAV” upside-down on the right side of the frame. Ainsworth-inspected, 4th Cavalry marked, Colt Single Action Cavalry Model revolvers are discussed on page 17 of “COLT CAVALRY & ARTILLERY REVOLVERS” by John A. Kopec. Kopec states that he identified 15 Ainsworth-inspected Single Action revolvers with the “CO.K.4.CAV” marking; the serial numbers of these revolvers range from No. 2902-No.4596. Kopec states that all of these revolvers were ordered by the Ordnance Department on January 15, 1874 and were shipped to the San Antonio Arsenal. The serial number of this revolver is not included in the 15 revolvers on Kopec’s list, as this example was found subsequent to the research. The revolver has a military blue finish on the barrel, ejector housing, cylinder, trigger guard, and back strap. ‘Feathered’ polishing marks are visible on the barrel on either side of the front sight blade. The frame, loading gate and hammer are color casehardened. The one piece walnut grip has an oil finish. The revolver has the early, ‘bullseye’, ejector rod head, cylinder with small stop slots and military style hammer with elongated, bordered knurling on the spur. The top of the barrel is roll-stamped with the early “Script” address: “+ “COLT’S PT. F.A. MFG. CO. HARTFORD. CT. U.S.A.+” in one line. “P” proof marks are stamped on the underside of the barrel and on the side of the cylinder. A “C” Colt sub-inspection mark is stamped in the hammer well above the firing pin hole. The left side of the frame is roll-stamped with the Colt ‘two date/two line’ 1871 and 1872 patent markings followed by the “U.S.” property mark. The inside of the loading gate is stamped with the assembly number “904”. The full serial number, “3576” is visible on the bottom of the frame, trigger guard, back strap, and the side of the cylinder. The full serial number is also stamped on the left side of the ejector rod housing near the rear ejector rod slot (this, in itself, is a rare feature); the numbers are smaller than the serial numbers on other components. All of the visible serial numbers match. The revolver is accompanied by a detailed description by Colt expert R.L Wilson which extensively quotes the descriptions of Ainsworth-inspected Cavalry Single Action Revolvers in “COLT CAVALRY AND ARTILLERY REVOLVERS”. Wilson states that this revolver will be used as an illustration in a forthcoming addition of “THE BOOK OF COLT FIREARMS”. Also included with this revolver is a signed letter from the late Ronald A. Ogan that states: “In my opinion, this revolver is the finest Ainsworth inspected, U.S. Army marked, Single Action known to exist”. The documentation also includes a detailed history of the 4th Cavalry regiment and the 4th Cavalry’s campaigns against the Comanche and Kiowa during the early 1870s under Colonel Ranald S,. Mackenzie. Extensive research and documentation is included with this revolver.