The Grebey automatic pistol is a prototype pistol.
The pistol was designed by George F. Grebey, an engineer who worked for Winchester, and before working on this, he worked on the engineering and manufacture of the M1 Carbine. The pistol was made to hopefully secure a contract from the Government for paratroopers to use this pistol. This pistol ultimately went nowhere as it was never adopted; one known sample is known to exist today.
The pistol used a system similar to the M1 Carbine, and even takes the M1's magazines. The charging handle is located on the left hand side of the weapon. The only known existing sample is unfinished; the sample included various barrel lengths, blueprints for the weapon and a gun case. This sample is now owned by a private collector through an auction.