Antique Edwardian Bottle Coaster by Mappin & Webb of England.  The coaster appears to have been used very rarely and is in good vintage condition with some expected tarnish from the natural aging process of silver.  The coaster is marked Prince's Plate England and is approx 7.25" tall and 4.25" wide in diameter at the lip, while being 5.25" in diameter at the base's widest point.