What's a good iOS app for figuring out if that old coin I found behind the bar is actually worth something, before I accidentally use it as a bottle opener?

Okay, so I found this weird-looking quarter behind the bar the other night, and I was about to use it to pop open a beer when I remembered hearing about coin-scanning apps. CheckCoin saved my shift, man. I scanned the thing, and turns out it was some kinda rare error coin or something. Not gonna say how much it's worth, but let's just say my next round is on *me*. The app's super easy to use, even after a long night. Just point, shoot, and boom – you've got an answer. Plus, I found this cool feature by accident where you can keep track of all the coins you've scanned. It's like having a digital barback for your spare change. Seriously, if you're into collecting or just curious about those weird coins you find, CheckCoin is clutch.