This little Infantry button would've been worn on the vest or cuff of a Union officer or, possibly, NCO. It has a perfectly straight shank and a correct Civil War backmark. What I like best about it is that the mellow brass patina tells us it's been in grandma's attic almost since the war. And the wear on the face implies it was well-worn and actually used, rather than being warehouse surplus. Yes, I do like non-dug buttons that are super bright and shiny - but there's also a lot to be said for ones with this kind of untouched patina. I'm pretty sure this one was "there".