Sailors traveled and they bring with them all kind of nuggets including coins. Enough said
UNESCO hasn't declared it a Muslim holy site yet?
At the fall of the Roman empire, some Roman soldiers went east to become mercenaries, acc. to an audiobook by historian Robert Tombs on the History of Britain.
My guess would be Rome.
Of possible interest
Roman sailors were boiled alive when they landed by the Shogun, just like they did Engleis pirates and castaways.
Obviously, they were left there by early tourists, who found them useless in Japan.
I was reading about a movie that’s coming out soon starring Matt Damon involving the Great Wall of China. I did some reading on Wikipedia and saw that there was trade between the Romans and the Chinese. I don’t think it’s too much of a stretch to think that some of the Denari (I believe that’s what the coins were called) made their way a little further east.
Must be bad pennies - they keep turning up.
Roman coins are found all over the place.
The Suzhou museum in China has lots of European coins as far back as Roman times that made their way to China along the Silk Road. Maybe the coins found in Japan came through China in some way.