Here is an image comparing two of the larger Colt rifle molds. These are usually seen in .56 caliber and cherried for both conical and round balls. Most of the observed specimens have a caliber marking (usually .56) and a single letter "factory stamp" on the side of one block. The blued mold in the image below is of the more common type and bears the .56 and "S" stamps on the side. The other mold casts two identical 50 caliber conical balls and is completely unmarked except for the Colts Patent stamp on the sprue cutter. It appears to have been finished "in the white" and would seem to correspond with the rare 50 caliber 1855 sporting rifle.
