Either tomorrow or Monday our time, Heritage Auction Galleries will be auctioning the Uncirculated Type II Adelaide Pound that was in the RBA auction conducted by Downies in November 2005. The coin made a few dollars shy of A$75k back then (equivalent to US$66k), and has an estimate of US$50k - US$60k. It is currently bid up to US$45k, so I reckon it obviously has some way to go before it is "on the market".
A strong result here will indicate strong international demand for historic and rare Australian gold coins, a less than strong result could mean that there is still strong international demand, just that it's not surging ahead. A sale worth taking notice of either way.