Here is an interesting story about a coin of Ptolemy IV found in Australia... http://www.abc.net.au/news/2018-06-02/far-north-queenslands-egyptian-coin-mystery/9708318
Ancient coins have been turning up in odd places for hundreds of years. Of course there are those who would have you think the Romans colonized America and other such nonsense, but it happens frequently. There has been a thread here about it. I once found a 1,000 year old Chinese Song Dynasty coin in the parking lot of my local post office.