Yep!!!!!
That type of button is a civilian button and is called a flat button or coin button. The backmark had another word or two at the top. It could have have been anything though. If you can see any other letters and let us know we may be able to figure it out.
Looking at this again, it looks like the word after Gilt is Standard. If so the whole backmark is probably Treble Gilt Standard or Imperial Standard, Treble Gilt