Isaac Newton Lewis is best known as the designer of the Lewis light machine gun, of course – but that was not his only work in the firearms field. In 1919, he patented a semiauto handgun using the same gas-operated, rotating bolt mechanism as the machine gun. It is a pretty massive steel beast of a handgun, and interestingly fires from an open bolt, despite being semiautomatic only. This is a questionable choice for a handgun, as it substantially hinders practical accuracy because of the heavy mass moving during the firing process, forcing the shooter to have exceptional followthrough to make hits.
That said, this pistol is very well made, and operated quite smoothly (except when the cocking sleeve rotates slightly out of alignment and prevents the bolt from falling). It even has a reversible firing pin. This pistol is chambered for .45 ACP, and is depicted in patents as having a double-stack magazine with a 15-round capacity. The magazine is missing from this example, but I am aware of another Lewis handgun of different design that does have a magazine of this basic type, so it’s not just a patent sketch. The gun is devoid of any markings, and I have no information on how many were made in total – but I suspect the number to be very low – possibly only this one.