The HP 1928 FyA 7,65 could be possibly for Argentina (1st choice) or for Turkey, as Hirtenberger was supplying Turkey in 1928 with both 7,65mm as well as 7,9mm cartridges. (Packets of both seen on Web several years ago).
Turkey at the time was changing over to 7,9mm, and the Packets were already in Roman Script. (Late 1928 was the change over to Western style script and the new western alphabet, designed specifically for the Turkish language.
Sadly late last year I lost the Computer Wallpaper of a full sized HP packet and cartridges…they were a red printed label on a buff coloured cardboard.
1928 seems to be a Big production year for Hirtenberger for export Military ammo…maybe the Treaty restrictions of 1919-20 were more often being evaded??? Definitely by 1930 Steyr was exporting arms again under various guises (“Steyr Mannlicher” and “Steyr-Solothurn”).
More questions, less answers…