Vince - Actually, the large primer pistol cartridges (all I know anything about) are not all that rare in the U.S. I have them in a lot of calibers, including .38 ACP/SUPER, .30 LUGER, and I don’t recall what all. Since it was either slightly pre-war or war-time commercial ammo, it is not surprising that not much of it went overseas. The overseas market was, shall we say, “busy with other things” besides sport shooting. Still, I think at this time it is probably wise not to shoot up anymore of it, as 65 years have passed since most of it was made, and there will be less and less of these specimens found as time goes on, of course.
By the way, I threw out a time-span there. In thruth, I am not totally clear myself on the exact time these were made. Some factories, like Remington, virtually ended commercial production of ammunition once we got into WWII (around early 1942, when military production really got going). It is possible that this ammunition was even made right after the war, with the large pistol primer being used in cases that normally had the small size, due to shortages of components and raw materials after the war. I guess a single primer for all was a pretty good idea uder the circumstances of a World War beginning, taking place or having just ended, so it could be any of those circumstances or the entire span of all of them.
Mabe someone who has given more study to primer can clear it up for us. I am primarily a student of the calibers themselves, and first above everyhting else, my interest is headstamps.
It is only in recent years, and on a small scale at that, that I have become interested in the more technical aspects, such as each component as a separate entity.