Phil - regarding the 7.9s that have red primer seals and green neck seals not normal to the country and date of the original rounds, these did come out of China. It is my personal opinion that they are not reloads, but rather simply sealed in China for whatever purpose. I have four instances of these same seals on the Western U.S. contract rounds with chinese symbols on the headstamp. In all cases the bullet is GM - three out of four are GMCS, with the forth being just GM and appropriate for the 1942 date. Original American loadings are found with GM and GMCS bullets in that date. The ogives are the same as the American bullets, and the domed primer is the same. My Czech one is headstamped “19 l Z l 40 l II l” and has a very thin red primer seal. It is easy to see that the primer is a flat brass primer with a green seal, underneath the red Chinese seal. Obviously the original Czech primer. The bullet is type s.S. CNCS of Czech characteristics. The bullet crimps on mine are untampered with and are consistant with the original country of origin. Why the chinese would simply reseal them, I don’t know. It is possible they replaced the powder also while using the original primers and bullets in each case, but the condition and style of the bullet mouth crimps makes that unlikely, in my view.
The headstamp on the Czech one is interesting because like the two you showed, the date is 1940, after the German occupation of Czechoslovakia. It is possible that these rounds came to China after the war and the Communist accession of power in China (and Czechoslovakia). It is possible, but less likely, that they were supplied during the war to Japan for the various 8mm weapons in use, including ZB zv 26 LMGS that were captured from China earlier, and then the ammunition was recaptured by the Chinese. I doubt we will ever know the truth of it.
Regarding the Czech SB and Z headstamps, in German style, that went to Sweden, we have the documentation of the box labels and a Swedish wall chart that I have in my possession, that show these rounds. No question that they were, at least in part, for Sweden. I suspect they represented partial payment of a trade balance between the Third Reich and Sweden. Not an unusual thing at all; we have done the same thing with Israel.
By the way, between you and Dutch, we are getting great pictures of some really good and interesting 7.9 stuff. Thanks!