Samuel Marshall registered his first mark on 18^th July 1799 as a small-worker.  He had been apprenticed to George Brasier, another maker of sugar tongs.  Tongs with his mark are rare.  This particular pair have the previous maker’s mark over-struck.  Perhaps Samuel Marshall did not make his own tongs, but bought from another maker when he had a customer wanting sugar tongs.  Notice how the maker's mark is over-struck