I call those "sand box" coins as the ones I've found were from playground sandboxes. The sand, depending on where it came from, will make clad coins that on that appearance. Ed. Note: be careful of kitty nuggets in that same sand. He,he,he,he,
Coins found in the sand at the beach do look that way also at some point. I'm guessing it's the salty environment that causes the clad to deteriorate like we see in the example on this thread.
