I thought sincere was from a later date-- and refered to alchemy--

where a small ball of gold was covered with some wax, and then rolled in lead dust. and the "alchemist" could make the lead go through "sublimations" of fire (with some magic words) and turn the lead into gold... (gee, i wonder how they did that?)

some alchemist were also con artist--and would "sell the secrets of turning lead into gold" and skip town before some on realized that in couldn't been done sincerely!

even if it dates from the ancient romans, it got a boost from alchemists!

my other obsession