The taxation matter is a (some would claim arbitrary at times) discretionary choice by the Australian Taxation Office about distinguishing between investment bullion, which is Goods & Services Tax free versus some other form of product which happens to be made of precious metal but in any case attracts GST.

More detail on this from the reputable and well connected 'Bullion Baron': http://www.bullionbaron.com/2016/06/screw-taxpayer-ato-compels-gst-on.html

I consider these to be a kind of Jerilderie Letter of Australian small mintage numismatic bullion. If you have or can get some they will be an esoteric & intriguing addition to a private collection, you can try to discuss and track them down in precious metals discussion & trade fora but a word of advice: don't try to hustle for them among Australian interest groups, such conduct will draw the diametric opposite of the desired outcome. It would serve far better to simply engage discussion on point of interest in precious metals and share appreciation and experience. If an offer or opportunity arises, well done, otherwise, you've already gained in the form of insight, possibly contacts, perhaps even friends.

Just remember that there is, still to this day, a fair measure of anarchic streak slumbering in the Australian psyche. Mateship can be made fast, and lost faster.

Words of Ned himself, from the Jerilderie Letter:

"I have been wronged and my mother and four or five men lagged innocent and is my brothers and sisters and my mother not to be pitied also who has no alternative only to put up with the brutal and cowardly conduct off a parcel of big ugly fat-necked wombat headed big bellied magpie legged narrow hipped splaw-footed sons of Irish Bailiffs or english landlords which is better known as Officers of Justice or Victorian Police who some call honest gentlemen.

"I give fair warning to all those who has reason to fear me to sell out and give £10 out of every hundred towards the widow and orphan fund and do not attempt to reside in Victoria but as short a time as possible after reading this notice, neglect this and abide by the consequences, which shall be worse than the rust in the wheat in Victoria or the druth of a dry season to the grasshoppers in New South Wales I do not wish to give the order full force without giving timely warning but I am a widows son outlawed and my orders must be obeyed."

Just my 2 Dinari's worth.