William Mason (January 30, 1837 – July 17, 1913) was a patternmaker, engineer and inventor who worked for Remington Arms, Colt's Patent Fire Arms Manufacturing Company, and Winchester Repeating Arms Company in the 19th century. Remington Mason began his career as an apprentice patternmaker, eventually working in the arms industry for Remington Arms. While at Remington, on November 21, 1865, he received U.S. patent 51,117, for a swing-out cylinder for easy loading and the star ejector mechanism to eject spent cartridge cases, a design used in 1896 by S&W for the .38 Hand Ejector (M&P and S&W Model 10). Colt Mason left Remington Arms in 1866 to work for Colt as the superintendent of the armory. Along with Charles Richards, Mason patented designs to convert percussion revolvers into rear-loading metallic cartridge revolvers. Those converted revolvers are identified as the "Richards-Mason conversion". After working on these conversions, Mason began work on Colt's first metallic cartridge revolvers in 1871: the Colt Model 1871-72 "Open Top" revolver was the third such pistol, following the .41 caliber House Pistol and the .22 caliber seven-shot Open Top. The Open Top .44 was a completely new design and the parts would not interchange with the older percussion pistols. Mason moved the rear sight to the rear of the barrel as opposed to the hammer or the breechblock of the earlier efforts. The caliber was .44 Henry and it was submitted to the US Army for testing in 1872. The Army rejected the pistol and asked for a more powerful caliber with a stronger frame. Mason redesigned the frame to incorporate a top strap, similar to the Remington revolvers and placed the rear sight on the rear of the frame. The first prototype was chambered in .44 rimfire, but the first model was in the newest caliber known as the .45 Colt. The revolver was chosen by the Army in 1872, with the first order shipping in the summer of 1873 for 8,000 revolvers. After the success of the Colt Single Action Army and Colt's conversion of existing percussion revolvers to Richards-Mason conversions, Mason went on to design Colt's smallest revolver, "The New Line" in 1874. There were five variants, each differing in size and caliber, but all using a breechblock designed by Mason. While Colt had first developed the concept of a "double-action" revolver as early as 1857 and a patent was filed, it was never