Aramis Antiques has dated this piece to the 1750s.
One possibility is William Grundy, known for hollow ware, and other possibles are William Turner or William Watkins. The caster has been cast in the classic Georgian design for this item, with a bulbous body, pedestal base and fitted detachable caster top. The caster top is pierced and bright cut, with a delicate ring turned pinnacle. The size suggests that this was a personal caster, for use by its owner. A very classic piece in excellent condition, given that it is well over 200 years old.
Aramis Antiques has dated this piece to the 1750s.
You can view the stock and full dealer information on the Aramis Antiques Profile Page