"Purple error" ? As in ' The Purple Penny' title .... Really ?! Colour of toning isn't an error. It was described 'blue & green'. Surely the auction house would have known about such an 'error' if it were one .... It carried an estimate of $10. - $20. Ended up at $2,304. !!! It wasn't described as something of a rarity ( and the auction house would have capitalised on any potential 'selling point' )
A check of Google produces no article on an Australian purple penny ( the only references relate to a private commercial venture of the same name ). If it were a recognised 'error', surely there would be some research or discussion about it ... I couldn't find anything. Thus, a 'purple penny' is merely a toned coin. I did find one reference that suggests, that bronze coins have been found to tone purple when stored in a 'tin can'- type container for some 40 - 50 years.
At least I was prompted to 'look into it' .... But the question remains .... Why was there a bidding frenzy up to $2,304 for a 1964 penny ???
Could be a pair of dumb and dumber bidders or money laundering if the same seller reaped similar windfall in other auctions. Ten percent premium to clean dirty money would be cheap.