It's one of a great variety of British metal buttons made from about the middle of the 18th to the middle of the 19th century. They had a big variety of descriptions written on their backs. TREBLE GILT like yours is one of them. I have also seen stars like yours and wreaths on the back. When the written back inscriptions were started they were designed to be a description of the process and the type of metal used in finishing them. But they soon became advertising slogans that seemed to mean that they were plated and that is all. Finding one like this tells you that either it was lost a long time ago, or that you are on an old site. If you find several in close proximity, it tends to indicate a site. It's a good find for you. The stars, I beleive, are just a decoration. Why they often decorated the backs of these types of buttons but left the front plain, I do not know.