Welcome to the forums. I think your button is a fashion one but without clear pictures of both sides it will be kind of hard to give you a date range. If I had to guess based on that picture and no further information about it I would say late 1800s. It would help us if you post a picture of both sides along with something to give us a size. Also anything you can tell us about a finds construction would help. Is it 1 piece or 2 piece? And it would help if we knew in what part of the world you found this.