Fish,
I can't find any reference to what they were used for. A 1937 B & M manual says: "Winchester or U.S.C. company No. 225 was a special size adapted only to certain Winchester and U.S.C. cartridge cases and is no longer manufactured." I suspect by that time the industry was standardized to the current sizes, as the old Winchester carts (38-55, 303 winchester and 405) call for the 8 1/2 or 115/120 primers. A complete list of primer sizes in that book is:
Large rifle (0.211) Rem. 8 1/2, 9 1/2, winchester 115, 115 1/2, and 120.
Small rifle (0.175) Rem. 6 1/2 and winchester 116
Large pistol Rem 2 1/2 and winchester 111
Small pistol Rem. 1 1/2 and Winchester 108.
I also have a 1931 Ideal manual, but it is sketchy on primer sizes, only saying to use the same size as the original cartridge used. I can find no mention of those Peters No. 65's.
Jim