[3] 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.

Following this, Mason once again teamed up with Richards to produce a larger framed version, the Colt M1878 Frontier in 1878.

Ehbets continued to perfect the idea for 7 years after Mason left Colt for Winchester.

[1] In 1885 he became the Master Mechanic at Winchester and held that position until his death in Worcester, Massachusetts on July 17, 1913.

[10] Winchester historian Mary Jo Ignoffo called Mason, "one of the most significant designers of the nineteenth century".