What happened to this coin?

Hello -

I came across this strange quarter and am compelled to ask , what happened to it in anyones best estimation. The color is not paint. It seems to be integral with the metal. I am not sure if it is an Improperly annealed planchette error . I really dont understand what the acid looking marks are caused by or the result of.

If anyone has a fair guess , I would be much obliged.

R/Chuck Wilson

The darker tone to it is quite common damage you can find on clad coins, just environmental. The brighter spots are likely from someone trying brighten it back up with household cleaning products / acids etc. A random guess as well but it could be laser damage too, Ive seen crazy people playing about online trying to melt coins and it leaves similar marks to what you have on yours. Hope that helps :) 

https://boards.ngccoin.com/topic/416382-2001-quarter-delamination/ 

A similar coin