Here is one of the more common Colt rifle molds. This one is marked .56 for the 56 caliber 1856 sidehammer Root revolving sporting rifles with either half or full stock configurations, and the military rifles and carbines of similar caliber. According to Robin Rapley in his book, Colt Percussion Accoutrements, the small letter (in this case "S") stamped on the side of the mold is a "single letter factory stamp".
