It's and 1850's to 80's New York button. From the detail on the face it looks 70'-80's period to me. If you can post a pic of the back that should help narrow down the date. If the backmark is Boylan or it has SNY on the back it is 1870's-80's for sure.
Awesome button Fats! Looks like the ones the Civil war guys dig up. I'm always surprised to see them dug in Michigan.
Looks like you still get away up north from time to time. So do I, not too far from you. I have a ghost town that would be interesting to check out, we should talk. My spots around home are drying up.