I assume it should have been a mint error during production of the 2 euro coin which has the "S" in one of the stars which shows. "The taurus and Europe", which is the only 2 euro coin carrying the "S".
It is the rarest coin I have come across. The fact that it is a mint error of an already rare coin makes it super valuable and collectible. This item is in the category "Coins & Paper Money\Bullion\Silver\Coins". The seller is "avramgr2014" and is located in this country: GR. This item can be shipped worldwide.