Coinsof1984@martinb6830 on twitter
Is that some sort of a souvenir coin from Greece?
It seems it is a New Year lucky token.
"Kali Chronia" is "happy new year" in Greek.
It may be from a Vasilopita cake - a traditional New Years dessert in Greece, which has a coin baked inside it. Traditionally a gold coin, but nobody can afford to give away a gold coin in a cake these days, so they use substitute tokens instead. Whoever finds the token in their piece of cake, gets a cash gift. Vasilopita tokens normally, but not always, bear a resemblance to British gold sovereigns (since that was the coin traditionally used).
A very professional packing for a coin won in an auction:
The perfect ancient coin for you!
My current "Box of 20"