Pat(Silverly) has discovered that there were two Mark Thomegays, one the son of the other.
23 January 1763
Mark, son of Mark Thomegay of Moorefields in the County of Middlesex, Gold Chain Maker was apprenticed to Richard Clark Needlemaker of London.
10 September 1763
This mark given in Grimewade must therefore have been for the elder Mark Thomegay, his father.
1 January 1769
Mark Thomegay went into partnership with his son, also called Thomas.
13 December 1779
Will of Mark Thomegay of Tottenham in the County of Middlesex proved at PCC London. His sons Mark and Richard are mentioned throughout the will. Reference TNA: PROB 11/1059/210
12 June 1829
Mark Thomegay, the son of Buckingham Street New Road Marylebone in the County of Middlesex will proved at London.
Perhaps we should call them Mark I and Mark 2 ?