1974 P Quarter Missing Clad Strip Or PMD?

@DECOIN The best for Nickel it is boric acid boiled at 40% acid. Sure if you shrub you will damage, but you do not want so after boiling for a 2-5 min (depending of condition) you soak or past in very hot water and job is done. Personally I dry with pression air.

Acetone on cooper change the color. Silver will be more flat or mat, the gold will change in reddish.

When I look at a coin I can say if was acetone bath in a few seconds. I do not personally consider restoration this, just damage because long term will show. Very old folks.

Sorry for the picture confusion.

Here you go:

Yeah I noticed that too. There's copper showing through the rim on both sides exactly where that copper streak would be if it kept going through the rim. Great call on asking for edge images. I'm now leaning more toward this being an actual mint error.

Thanks for the extra images. IMHO, it does look promising but this is probably one that would need to be sent in to someone for an in-hand look. The difference between damage and error can be subtle.

As silviosi correctly concluded, this is a stain.