The official name of this is the Model of 1940. It was developed and produced for the British government during WW II. Production was in 1940 and most of the guns shipped to Britain were subsequently destroyed. The reason for that was that the gun was designed around the weaker US 9mm loading and not the hotter European military loading. As a result, the guns failed to pass testing. About 130 of the original production guns remained in the US. Subsequently, S&W developed and produced Mk II version, which was supposed to fix the deficiencies in the Mk I. Those too were destroyed after the war.
In 1974, a number of new, unfired, and crated rifles were discovered in a S&W warehouse. No number is listed, but it might have been the 80 Mk II guns retained in the US. (That's my guess). They were sold as C&R guns to a distributor.
My information comes from a quick reading of the information in the Standard Catalog of Smith & Wesson. There's not a lot of information there, but there is some. Total production is listed as 1227 guns. There are very few left, mostly in museums.
S&W has an official historian, Roy Jinks. He's well known for his factory letters detailing information about handgun production. Letters cost $75.00 last I knew. I've seen them on line and they have some background of the model and then specific details about production date, configuration, and to whom they were originally shipped.
Again, I don't know if he will do a letter about this specific model, but it might be worth contacting him.
That's an interesting piece of history you have there. Over the years, some one off specimens of various S&W firearms have ended up in the general Springfield area. Prototype handguns, salesman's samples of handguns that were never cataloged or offered for sale, and even one of a kind firearms for special customers, sometimes end up in western MA gun shops.
