Spain: 25 ptas 1982 - Worn lamination

How thick is the silver coating (cupro-nickel???) on Spanish coins?  I have one that appears to be heavily worn on the Obverse only, but with very little of the relief detail missing.  Other than the obvious wear, this coin seems to be in quite good condition.

N#428

Is this a common fault?  Possible forgery?

Silver coating? It's a copper-nickel coin, same composition throughout.

Yeah I think OP means silver colour coating or just the coating as it is less silvery underneath that coating (which is silvery) 😂

More of a brass/copper colour actually, which is why it's so obvious.  I've not seen this before, so thought I'd better ask why.  It's almost as though it's been lightly sprayed with shiny silver paint, or more likely electro plated, the worn coating is so thin.  That's why I suspected it was a forgery.  

Anyone else got a 25 peseta coin with similar wear?  Normal/Forgery (???)