Hi Ray,
Made in both countries, there appear to be no uniquely Australian models made by Sheaffer although I've heard it said there was a unique Aust. Snorkel but I've never seen anything that's not standard. While Sheaffer (Aust.) had a fairly large and diverse range Sheaffer (US) certainly produced more models, especially the high end, in a lot of lines. The lack of any Sheaffer literature relating to Aust. means it's just a matter of waiting to see what models turn up, yours in one.
Regards
Hugh