Besides Colt, during WW2 Remington-Rand (typewriter manufacturer), Union Switch & Signal (railway signal manufacturer) and Ithaca made 1911A1s in volume. Ithaca was the only gun company besides Colt that made 1911A1s.
Singer was a sewing machine manufacturer.
Popular folklore is that there are more "Singer" marked pistols available today than were ever manufactured for the war effort.
It might interest some of you to know that one of the firms that made the M1 Carbine was Rock-Ola, of juke-box fame. It was said by the GI's that the Rock-Ola carbine 'played the prettiest music this side of a funeral'.