1975 D Dime Split Rim

yup, an acid coin. We see this all the time. I have one as well

I have one as well. I was going to post all photos when back home I only have a edge shot with me but the face of the dime is NOT etched. Sorry no date or other information. I will post fully when I can but it will be a while. Any other possible cause for edge

Almetzger3, you really should post your coin in a thread of it's own.
Having said that, yes, your coin is suffering from acid damage as well.

depends on the acid used. a clad dime is 75% Cu and 25% Ni over pure copper core, if the acid is strong enough to eat pure copper, but weak enough not to touch CuNi or nickel, it will just dissolve the core along the edge long before it starts corroding the cladded surfaces.

like for instance, you can scrape the edge a bit to expose the zinc core and put a zinc cent in muriatic acid it will eat away the zinc core and leave behind a hollow copper foil of the copper plating. it can't be done this way in reverse to strip off the copper because whatever acid it would take to dissolve copper, would make light work of the zinc, but there is a way to de-plate a zinc Lincoln Cent and leave behind the copper core.

Anyways it's the same principle.

there's also shrinking coins with magnetic fields, and enlarging coins like "texas cents" by hammering a coin between leather to make it bigger.
people been damaging coins for entertainment as long as there has been coins I think.

You guys know so much about anything I come across always impressed thanks for the comments!