That bsoviet Ammo was acquired by Sam Cummings (interarms) from various Central European source he did business with, i8ncluding “Omnipol” the Czech Export trading company (Tractors, ammunition, Heavy Machinery, guns, etc.) The Repacking could have been done in Finland (IA did a lot of Milsurp Ammo remanufacturing there, both of Finnish and German and British ammo) or in Britain (IA had a base in Manchester for “Trade Proofing” all the Lee Enfields and No4 rifles etc. he bought from the British Govt; as well as his Major Warehouse of guns from all over the world, before sending them to the USA,Canada, Australia, etc.
SC’s connections with the CIA also served to move (Both ways) quantities of “clean” ammo ( source not verifiable) and guns of a WW II nature for the operations undertaken by the CIA.
Now as to the differences between the 7,63x25 Mauser (1896) and the 7,62x25 Tokarev (TT30). CIP and SAAMI specifications vary slightly in neck length, exact OA case Length (the 7,62 Tok, in steel, is slightly shorter ( 0.5-0.7mm). BUllet diameter is the same (.309-310) and Powder charge is “roughly” the same but of different Powders. Whilst DWM original 7,63 M ammo was loaded for a Temperate-tropical climate range, the Russian was loaded for an Arctic-subarctic Temperature range, to ensure it worked in Winter…hence in summer, it will rate a higher Pressure than most "DWM Made 7,63 M). I have found that Both Russian and Chinese 7,62 Tokarev, regularly Hammer the Bolt Lock and its receiver slot shoulder, in some guns quite dangerously…Hence I now use only Handloads and the occasional FNM-Century Arms Contract 7,63 Mauser ammo. Steel cased Soviet and Chinese is much worse than Brass ( early 1950s Brass Tok ammo, was made on the same machinery that originally made 7,63x25 for the Chinese Nationalist Forces. ( Factory 321, “Experimental Pistol Cartridges 7,62mm” with a .199 primer (Berdan), brass case, and very dirty Powder 1952-3). BY 1956, China was making all its mainline ammo (7,62 Pistol, 7,62M43, 7,62 T53 ( x54R) IN Copper washed steel. The Steel cases don’t adhere to the chamber like brass does, so the Breechblock opens well before the pressure has fallen, and hence the high recoil velocity and Hammering of the Bolt Lock in C96 Pistols. It does not matter in a PPSh or PPS, but it sure does in a Mauser.
BTW, the Russians wanted “Socialist Order” in their calibre designations so the Tokarev Cartridge was Named “7,62x25 Pistolet/ Pistolet Pulyemiet Patronnyi…” ( Pistol and Machine-pistol Cartridge)
OK, so the Russians invented the Telephone as well…