1989 Roosevelt Dime, Copper?

check the weight.
A dime weighs around 2.27 grams. Each clad layer weighs approximately 0.4 gram while the core weighs around 1.47 grams.

you would be looking for a weight of about 1.47 grams for that to be missing the clad layers on both sides, and it would be visually thinner also.

I'm 99% sure from the picture it's environmental staining/damage. it looks to be the right thickness, but check the weight to be sure and rest your mind about it.

value would be 10 cents, just a stained dime.

It still has some sheen to it, and there is no sign of any kind of deterioration that the elements cause. I don't think it's any kind of environmental damage, nor painted or stained. And with jewelers loop, you can see it's one material by a nick on the rim.

Would a copper dime weigh the same as a normal dime? Cooper pennies don't weigh the same as zinc.