Thanks Nancy. It is Vernon's Patent China and Glass Company Limited, which occurs as china manufacturers in a Trade Directory of 1884 at an address in Wharf Street, Stoke on Trent, Staffordshire. On the backstamp they claim to be of London. It appears the company was dissolved in 1905. It does not appear to have been a famous business!
The crest is a Pelican (not swan) winged in her nest feeding her young. The motto is Virescit Vulnere Virtus - Courage grows strong at a wound. This is the crest and motto of the Earl of Galloway and Clan Stewart, which suggests that Vernon's had a Scottish connection with that family or clan?
It would be interesting to see an image of the pattern on the face. There may be interest to add the maker and pattern to the database.