Manufactured in 1878, the first year of production. The barrel has the scarce "COLT'S PT. F.A. MFG Co HARTFORD CT. U.S.A. DEPOT 14 PALL MALL LONDON" address and is chambered in .450 Boxer. The trigger guard is marked "45 CAL/B." Reportedly 406 Model 1878s were manufactured in .450 Boxer with a 5 1/2 inch barrel and nickel finish per Don Wilkerson in "Colt's Double-Action Revolver" (354). London proofs are stamped on the underside of the barrel and behind each cylinder flute. The cylinder, loading gate and both grip panels are numbered to the gun. The partitioned case features a Colt London paper label on the interior of the lid and contains an added cartridge block holding 24 rounds of .450 caliber, cleaning rod, tool, James Dixon & Sons oiler, and case key.