Uberti 1872 Open Top Late Model Army 38 SPL 7.5 "BBL 341351 NIB 38 Special. In 1872 Colt entered the market for metallic cartridge revolvers by introducing their factory-installed percussion-to-cartridge open top conversion of the 1861 Navy cap-and-ball revolver, followed quickly by the Richards-Mason conversion of the 1860 Army the following year. Based on a patent held by Colt employees Charles Richards and William Mason, the old cap and ball cylinders were cut down at the back to allow the installation of a conversion ring to accept metallic cartridges.