Japanese made 7,9 cartridges for Type 98 (MG17) aircraft guns

I have several Japanese made 7,9mm Cartridges from New Guinea found near an old Japanese Air force airstrip.
The cartridges were ID as 7.7x58 T99 rimless, but the three stab primer crimp and the shorter case said “7.9 T98” to me. No headstamp.
Has anybody got any info or packet labels referring to
This Cartridge? Japan used both imported German MG17s and made their own clone called the Type 98
(1938).
The use of 7.9 ammo by Japan seems a forgotten part of its ordnance history; the army used a lot of captured Chinese 7.9 MGs (ZB26 & T24 Maxim) in China and also elsewhere early in the war…
Doc AV

The Japanese army and naval air forces both used a Japanese version of the MG 15 as a flexible gun for aircraft. The ammunition produced for the army used the German style three stab crimp while that for the navy used, I believe, the large primer the navy was already using for their .303 ammunition. Ken Elks’ book goes into this matter in some detail but isn’t at hand just now. Jack