Rainbow colored coins

[westkybanded]

Going through the office penny jars helping my son get his Harris books filled up, and came across a 1973D with the most amazing rainbow coloring I've seen. I've noticed it on a few other coins in the past but this one was striking.

What causes this? Do these colored coins ever command a premium?

 

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[Mackaydon]

You might find this article interesting:
Rainbow Toned Coins - Fake or Real | eBay
Don.......

 

[westkybanded]

Haha...

I can't see anyone artifically doing this to a 73 penny... Maybe I'm wrong.