Odd 1978 Ecuador 20 Centavos

What is going on here. If it wasn't for the edge of the coin I would think it was plated somehow. But see the edge pics.

Any thoughts????

It looks like the kind of oxidation caused from having been a long time in a plastic coin folder.

I see in the catalogue that this type is nickel-coated steel. It looks to me like the edge was not coated, but I don't know whether that would be an error on your coin, or a regular feature.

Any other thoughts?

Found another coin from the same supplier...this was is a Colombian 10 Centavo....what the heck are these from?

To fool vending machines maybe.....? Odd!

Caused by chemical leeching from a cheap coin holder?

Wow

This is yet another nickel clad steel:

https://en.numista.com/catalogue/pieces2434.html

so it looks like what I was saying about the other coin may well apply to this one as well. Perhaps they were kept in plastic envelopes in a humid environment?