AIA is listed as a manufacturer and wholesaler of firearms. Previously they were known as Australian Collector Arms, apparently founded in 1993.
It seems they are an importer of rifle parts into Australia. So, there is the company and importer. The parts are outsourced primarily around the Pacific Rim. Earlier rifles had pieces imported from England and the US among others.
Like WW2 British and WW1 peddled scheme Lee-Enfields, components are sourced from a number of countries. Some parts come from South East Asia, just as some parts originated from England and the United States.
Good hardwood at a reasonable price is not easy to find. AIA has used plantation Teak from New Guinea, Brazil, West Africa and Laos.
Skennerton makes a good analogy in his book.
" Consider that a product made in a free trade zone in Mexico can be marked "made in the USA". An unfinished action body can be imported into North America with only one of two cuts not done, yet is can still be marked "Made in the USA" after the final machining is done. "
So these parts could have come from any where really and we'll never know. The parts can be labelled by the maker to the tune of what ever the destination company likes.
My research can not verify that any parts were manufactured in Vietnam. Having said that, I am not well versed in detailed investigation methods. Just what I can find and read. (S.Redg, I. Skenn).
I'll bet you that Remington, TC, FN USA, etc.. imports some parts from Asia too. Regardless I don't think anyone should be calling foul. If you're bothered by the possibility don'y buy one. I for my own reasons refuse to purchase any Chinese manufactured firearms. Thats my personal decision but in the end I'm probably buying firearms that still have Chinese made parts in them.
I find this global market stuff extremely disorientating