Manufactured from 1850 to 1851 with total production around 1,000. Production was halted due to a patent infringement suit won by Colt. "WESSON'S & LEAVITT'S PATENT" marked on the action, patent marking on the rear cylinder face and Mass. Arms address on the top strap. "377" is marked on the top strap lug, "1" is marked on various other parts, " and "4" is on the butts of the grips and toe of the backstrap.