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.
Grant Hammond .45 Trials Pistol: https://www.full30.com/video/d704a9b1c364dad9e9738ea76d2b8397
Savage .45 ACP Trials Pistols: https://www.full30.com/video/dbb3150fa725fc12a117daad78fc189c
Shooting the .45 ACP Savage: https://www.full30.com/video/c2ca864d9dd1c1acc73189a6d364ed28
Knoble .30 Cal Trials Pistol: https://www.full30.com/video/4c01a38dd57f6078f049b178f934e2f5
Schouboe .45ACP Pistols: https://www.full30.com/video/9e08e89f2b288fb3af95af60ef28eab4
Pieper .45ACP Prototype Pistol: https://www.full30.com/video/f1e510114d72b4af22259fa9c3f180e1
BSA Prototype .45ACP Pistol: https://www.full30.com/video/048e00a1186971f92db6f097a8fc3882