The use of APRIOR sigma marking in 1970s Patek
By: Franco : July 7th, 2020-09:53
Hello have read that the APRIOR consortium introduced the use of "sigma-swiss-sigma" on dials of swiss watches from 1970-1971. This was to indicate the use of golden indices in the dial. Have recently come across this (picture below) in a ref 3445 white g...