It's what's called a trade token or piece of scrip. In the late 1800's and early 1900's merchants issued these tokens to customers as a form of advertising. J.D. Brown is the name of the merchant who owned the store that issued your token and you could only use that token at his store. It could have been a general store, grocery store, drug store, bar or just about any thing you could think of. It also could have been issued by a company - such as a coal mine - to it's employees to be used only at the company store. I found one myself just the other day. Brass tokens are older than aluminum ones.