For Chemistry, I have to design a coin. What are some anti-counterfeiting measures I could use to prevent people from replicating it? I've googled this, but I haven't found many good ideas. I can only think of putting grooves on the edge of the coin and, and making it of an alloy so it's more difficult to replicate. Do you have any ideas? Thank you.

I found only one reference and it is limited. Frankly, crooks can't get too excited about forging coins because it's a lot of trouble to make a 25 cent piece and not much profit. That's why (I think) that forgeries are made more of paper bills. For coins, the ones made of bi-metals may be the hardest to forge; crooks have forged "rare" coins since they are worth much more money. Th ridges on the edge of coins is also used to keep forgeries down.

http://en.wikipedia.org/wiki/Coin_counterfeiting