Hammered Silver Groat

It's about a U.S. dime size. Thanks for the info, I was just guessing it was British.

I'm not entirely sure what it is, but I can tell you it's definitely not English, or anywhere else in Britain, either. Nor is it "groat-sized" - groats were typically about the size of an American quarter, and at least one side of a groat had a double-ring of legends around the outside.

It's what's on the other side of the coin that confirms this. British pennies all have portraits on the obverse. This coin does not. The design of this coin is a classic "denier tournois" or "penny of Tours", based on the coinage of emperor Charlemagne and used by numerous Frankish successor states in Europe and by the Crusaders in the Holy Land and Greece. The little crosses in the legend are at the top, so here is your coin, right way up:



Compare it with the pic in the Wikipedia article. The reverse is on the left, with the legend around the cross +TVRONIS CIVIS - City of Tours. On the right is the obverse, with the "castle tournois" in the middle and the ruler named around the outside. I think it's an abbey coin from the abbey of St Martin, near Tours, one of the wealthiest abbeys in France at the time. Here's an abbey coin to compare it with. Unfortunately, I can't read enough of the obverse legend to be absolutely sure.