silver blank not sure what coin or value?

Are you sure it's silver? Looks like a knock-out from an electrical box?
John1

is it unusually thin? It could just be a very old coin worn completely smooth.

I can just barely make out some lettering around
the fields near the edge. Betcha a sanded down etc.
Wash. quarter. Reeding was also taken down.
That would then make it in the current weight range as well as the diameter if so.

Take some Mothers or SemiChrome polish
and polish the heck out of it. Would look nice
anyway.

So how did you test it to ensure it was silver?

@Jayman931, when I used to test world coins for silver content, I would use Silver test acid... The only way you know what type of metal you have is to follow the instructions and file a "Deep" notch on the edge of the coin, then place a drop of acid on the notched area and check the chart color... If I understand what I am reading, the poster mentions a rubbing on a "test stone" and testing atleast 90%... When I read this I know that this is not the correct way to determine the finess of silver and wonder what color he claimed to see on the test stone...