I'm inclined to believe there were LOTS of frames on hand when the War ended. Remember- the Gov't had been real testy about getting orders on time, and S&W REALLY wanted to avoid having the plant nationalized AGAIN. Also, remember that the last contracts of the War were cancelled when Japan surrendered. So, I'm thinking they had parts!
Think about it for a minute- do you really think they were building frames, drilling a swivel hole AND crosspin hole, then making plugs, installing the plugs, and sanding them smooth? Duhhhhhhh...............don't you think somebody would have been smart enough to yell "YOU GUYS QUIT DRILLING SWIVEL HOLES!!!!!" ????
