We have this very nice two-handled cup. The marks are for London 1769-70 and the maker is John King (Grimwade 1445-6). There is also a photo of a John King mark in Jackson (p. 213) for a tall coffee pot and dated 1769-70.
The marks for John King(Grimwade 1445-6), were entered in 1775.
Was it common practice for silversmiths to be using their mark before registration?
Grimwade (p.571) does make mention of another John King who was apprenticed to George King.
I look forward to your input.