According to the seller of this auction item on eBay, this key to City of Adelaide was obtained directly from legendary, award-winning, supterstar.
The seller says, "A very unique item from Cher's own personal collection! This engraved plaque and brass key to the city of Adelaide Australia was presented to Cher in November 1990 Includes original box Hand-written sticky note on box: 'Mementos'."
According to news reports, the fine Aussies of Adeliade are pretty steamed about this auction. See below.
To own this key, click the link and be prepared to place a jaw-dropping bid, Mr. 1 Percent.