The plumb law took affect  in 1985. The "P" mark, standing for PLUMB,was used by jewelers for 5 years (1990) to allow the 13 1/2 kt. and the 9 1/2 kt. gold  to be identified. In 1991,all 14 kt and 10kt. (KARAT) not CARAT(used for gems olny) had to be .583 %  or 41%  .999  fine gold. If you supply your old gold and the jeweler uses it, he is not required to put any karat mark into the mounting. After all,the jeweler doesn't really know what you have supplied them.