This is an exceptionally rare example of an extremely early production factory engraved Colt Model 1851 Navy percussion revolver that was manufactured early in 1850. The revolver has the distinctive square back trigger guard, wedge notch on top of the cylinder pin and wedge screw located beneath the wedge that characterize the first 1250 Model 1851 Navy revolvers. The frame has the wide capping cut-out with no capping channel. The top barrel flat is roll-stamped: "-ADDRESS SAML COLT NEW YORK CITY" in a single line. "COLTS/PATENT" is roll-stamped in two-lines on the left side of the frame. The cylinder is roll-engraved with the Texas Navy battle scene and "COLTS PATENT No". The serial number "613" is stamped: (1) on the bottom of the barrel lug, (2) bottom of the frame, (3) bottom of the trigger guard, (4) bottom of the back strap, (5) top of the wedge, (6) side of the cylinder and (7) underside of the cylinder pin. All of the visible serial numbers match. The revolver had a blue finish on the barrel and cylinder, with casehardened loading lever, frame and hammer. The brass trigger guard and back strap are silver-plated. The one-piece walnut grip has a high polish piano, finish. A small punch-dot is stamped above the serial number on the barrel lug and below the serial number on the frame, trigger guard and back strap. Colt used the punch-dot to identify components that would be engraved or designated for special finish. The barrel, loading lever, frame, hammer, trigger guard and back strap are engraved with incised or intaglio scrollwork that was executed by Joseph Delany. Joseph Delany engraved a number of Colt revolvers from 1850 thru 1852. A Colt Model 1851 Navy revolver with nearly identical intaglio scrollwork attributed to Delany is illustrated on page 37 of "COLT FACTORY ENGRAVERS" by Herbert G. House. In addition to the scrollwork engraving the inside of the grip strap is inscribed: "G.N.T." to "E.A.R." in flowing script letters. Factory engraved Colt Model 1851 Squareback revolvers are very rare and the first style "wedge over screw" variants are almost non-existent!