William Mason was a prolific inventor, working at various times for Remington, Colt and Winchester. He held many patents on firearms and others on machinery and tools. He also operated a shop of his own where he made guns. He patented this side swing loading and ejection system 21 November, 1865. This prototype of a revolver with a cylinder which rotated to the side for the loading and unloading of the cartridges, was built on a converted Remington double action Belt Model revolver. There are no Remington markings on the revolver except the original serial number under the left grip. The front of the frame was removed and a new one with added bulk for the pivot screw in front of the trigger guard was added. The cylinder, which was converted by removing the rear and adding a bored through ring, also had an extractor star added with the pushrod acting as the cylinder pin. Unfortunately for Mason and Remington , Smith & Wesson's Rollin White patent on the bored through cylinder still had several years to run and they could not make any revolvers under this patent. The loading gate and frame addition for the pivot screw were probably done in Mason's shop. The ejector rod under the barrel operates the ejector star at the rear of the cylinder and ejects all of the cartridges at the same time.

Very good. 50% blue on barrel and cylinder, 20% on frame. The grips and pivot screw for the crane are replacements and needs pivot screws properly replaced to hold cylinder in position, otherwise very good.