I recently made some alterations to a friend's coat and realized that there was a small button affixed on the underside of the fabric, so the jacket kind of had a button sandwich going on. There was also kind of a rubber gasket thing that the thread ran through between the visible button and the jacket fabric. Does either thing serve some kind of benefit? i.e. From the outside in: main button --> gasket thingy --> jacket fabric --> small button (all affixed with the same stitches).