Really, really interesting, and a great result.

Did you think of using a dedicated "wash" paint, designed for model figures? Citadel (the brand name used by Warhammer) have an extensive range of washes in different colours from black to brown to a dull yellow? They give a similar tint/aged effects as your strange mixture.

Coincidentally, I went to the Art Under Attack exhibition at the Tate Britain, and there are a lot restored masterpieces that brought back to historic condition after being attacked for various reasons (usually religious, political or random). Your watch fits the restored masterpiece theme ;-)

Btw : very interesting exhibition, I'd recommend it