Have you ever thought if Tommy Gun is the M1 submachine gun, why the Grease Gun is M3 and not M2? Well, because there was an M2 SMG which we are looking at here. Designed by George Hyde, this SMG was supposed to be a cheaper to manufacture, simpler and lighter-weight gun to replace the Thompson submachine gun. And in fact, it was quite a good design.
Although this SMG was actually adopted by the US military, it wasn’t manufactured in any significant quantities due to some issues with setting up the manufacturing process. Marlin was granted the contract to manufacture the gun but by the time they started delivering the M2 SMGs, the contract was canceled, because by that time, the same designer, George Hyde, has developed the “Grease Gun” which was a much cheaper to make SMG and was adopted as the M3 submachine gun.