Is that a rattlesnake button with 13 eggs? I don't know buttons, but I think that could be an oldie and a goodie! Don't listen to me though, I would wait for others to post.
And thanks for the posts already. Shows how much I know I was about to toss it thinking it was just a button from some old jeans. The only reason I kept it was because of the depth I dug it at I was never even thinking military!