The TPGS's call it "environmental damage." Ever see a "brown" Buffalo nickel? Same sort of thing, only looks different. Put a new 2016 dime outside in your yard and watch it over the year.
This dime look like it was in the lint trap of a washing machine. After lengthy time with loads of expelled laundry water rushing past it they look like this. I have a few I've actually removed myself from such a place and they look just like yours.
Wonder why people post these BEFORE slapping them on a scale?? Nothing against you OP, I just think , that most folks would not bother posting .If they weighed there dime 1st, and it weighed 3.1 or 2.3, heck .I guess I don't even know what a clad dime weighs, so .NVM I guess
The truth is that I don't have a scale and I would rather get the information from people that know. I like to learn and this forum is a great place to get knowledge.
looks kinda like what happened when I put some clad coins in a mix of peroxide, vinegar and iodized salt solution. I dont recommend doing that to anything of value just so you know lol.
Why exactly would I do that for??? It is on a small led light. I can see how that could be conceived as a urinal, I guess.