I came across a "WB" inspected Colt M1911A1 at a gunshow Saturday in 99% condition. Serial #779xxx. Finish grey green parkerizing and appeared original, with burnishing marks on WB in box and verified proof on triggerguard. Arched checkered mainspring housing, checkered slide release and checkered wide spur hammer. Correct Colt .45 marked barrel on left side with P proof. Price was $1400, but now the question: The slide, while grey green parked and crisp original finish matching frame, had commercial markings, vintage 1942 and did not have any serial # behind firing pin stop. I know they used commercial slides in certain serial number range USGI pistols, but this does not appear within that range. Also, the lack of the serail number behind the firing pin stop on a 1942 vintage pistol made me walk away from it. I took the dealer's card just in case. But, does anyone know if this pistol could be original as described, or is the commercial slide a later switch?