James Harmar probably had marks in the lost register as Heal gives a James HARMAR, Silversmith at Ship Yard, Temple Bar in 1747
Inland Revenue Board of Stamps transcript 171/205 of 1746 records the apprenticeship of a James King , son of James King to James Harmer of St Clement Danes ,Goldsmith . Some of the Kings appear to have been bucklemakers, Harmars apparent speciality.
Westminster Pollbooks: Votes in Westminster Elections, 1st January 1749 - 31st December 1749 records that James Harmar, Goldsmith of Ship Yard ,St Clement Danes and St Mary-le-Strand voted for Trentham .
All the above could of course refer to a separate James Harmar.
The surving incidence of his marks on buckles and nips suggests that he was not active much, if at all, after his appearance as bucklemaker in PR1773, so it may well be one man.