This is due to the copper effect. 18KT gold is mixed with silver and copper in order to make the gold harder and more wear resistant than pure 24KT gold.
I notice that the day/date wheels for the 18k model of both 3711 and 3713 have patina or become yellowish, but not for steel model, anyone knows why? Many thanks! PS. pic not mine ...
this case it could be that from 25% of other metals, one of the metal used is dominant or high dosage of it (here probably copper) and helping this patina effect. I like this watch ;-)
This is due to the copper effect. 18KT gold is mixed with silver and copper in order to make the gold harder and more wear resistant than pure 24KT gold.