The rate to Zone C (which includes Australia) from 3 October 19966 to 15 February 1971 was 10d, so this is a good and not easy to find solo usage of the 10d Machin. Not easy to find in Britain, but maybe easier in the pacific area? So how did it fare?
It's not perfect with a few rust spots around the stamp and airmail label, but otherwise quite good for a postcard. From a starting price of £5, it remained at a low level until a bidder came up and tipped it through to £20-ish. That bidder seems to have dropped out, being outbid by the early bid of £100. But even that was not enough as a late (snipe?) bid for £102 won the day. The seller is located in the UK; bidding is hidden, so we cannot tell where the buyer was.