Is that all S&W produced? I would have guessed they made other items also. If not completed goods perhaps just parts for others? It could even be mundane things like springs or washers. They did have heat treating and plating lines. Some places just did machining of sub assemblies.
Some years ago I was very interested in the war production, war board and how and what different companies made during the war. Its a fascinating part of history, almost anythings possible!
As a cash register dealer,and collector of antique registers, I always found it interesting that NCR built the Norden bomb sights.
WG28, It kind of worked the other way around. Look at garands, carbines, M-1911A1's, Model 2 HB's etc. etc. and those companies that got into the gun business during WWII. Not to mention heavy equipment, aircraft, shipbuilding, automotives etc.
An interesting transition was Kollmorgen who built periscopes. They bought Redfield who made precision iron sights and took them into scopes.
That S&W was knocking on their middle millionth M&P in a 5 year frame, and turning all their production to a single model, all the while recruiting, training, expanding is for me impressive enough.