That could still tell us something right now it sounds like the back was probably tin or some other type of metal which immediately makes me think it's from the early 19 hundreds onward.
Is there rust on the back?
What other items were found close by? What's the history of the site you found it? If you want the best answers giving all possible information is the best way to go
Now this is only my opinion but being that it's a civilian button the possibilities are enormous.. The best I could do would be to say it's a civilian garment button from most likely 1920ish to 1950 ish.