Ping
They can show a no earlier time - because of when they were minted.
But that later date? If I drop a 1958 dime in my back yard it doesn't mean the house was built then.
Surely no one believes Cook was the first to Australia. When Cook returned to England making that claim, Commander Dalrymple of the British Admiralty protested vigorously, as the Admiralty had excellent maps of Australia that were already 250 years old!
Said coin could have been dropped by anyone, from the date it was minted, to recent times. You need far more than a coin to establish the landing of a vessel.
Traditionally a party landing on new or unknown beaches would attempt to erect something more substantial than dropping a coin in the sand.
Fascinating post, thanks!
There is a local historian (Waiatarua, New Zealand) who has claimed that, based on petroglyphs near Taupo, the Phoenicians had discovered both Oz and NZ and had established viable settlements in both places, round about the time of the great Taupo volcanic explosion.
While this sounds far out, his theory is plausible, and the petroglyphs near Taupo require explaining to the contrary. No Maori ever carved them, and one appears to be a fairly adequate map of the world (with huge allowances for perspective).
Others say the Celts were here first, and there are good reasons to believe that this could be so, too.
I have no difficulty believing his theory. The Phoenicians, the Vikings, the Celts were rollicking good seafaring stock who thought nothing of launching forth into the horizon in seaworthy contraptions, perhaps destined to never see home again and settle where they may.
So why not? The plain fact with Oz and NZ it was a case of finders-keepers-losers-weepers, and it matters not tuppence who found it first: the Brits kept whatever they found and settled it efficiently.