It is pretty well accepted that in real copper rims, the outer edge remains with a brass color after minting.
What I don't understand is, if the reddish color is a result of different percentages of the relevant material in the "mix" than what is normal, why should the rim edge end up with a different color than the sides?
Thinking about it a little, I guess we really don't care. What is, is....just wondering.
Anybody out there with metals background care to give us some insight?

Last year I bought one of the supposed Silverton "coppers" from someone at a show. I only paid $25 for it...more than I cared to risk...but I wanted to test it at home.
It passed both tests for validity, but inside, I still can't make myself believe it could be real. I never did believe the Orleans, Silvertons or Slots-a-fun's could've possibly been made, but realistically, the mint didn't care about color, so a worker could've easily picked a few stray rims off the floor and just threw them in with a new batch in the process of being minted.