This is an extremely good quality 19th century table  wine/ bottle/ decanter coaster, very likely to be by James Mein of Kelso, Scotland. It is made of solid mahogany beautifully turned with lovely deep lappet- carving. The underside of the base is fitted with three brass and leather castors so that it can be rolled down the dining table without scratching the surface. around the rim.
It measures 23cm w and 16cm internal diameter.