Oxidation-Reduction reactions involve the transfer of electrons from the oxidized element to the reduced element. The mass of an electron is so small 9.109×10−28 gram The measurement would not be noticeable.
Oxidize a hydrocarbon to carbon. The hydrogen goes away as water, resulting in a loss of approximately 1/7 of the hydrocarbon's original mass. Oxidize it some more, to water and carbon dioxide, and it all goes away. Reduce a ketone to a secondary alcohol; it gains the mass of two hydrogen atoms. I'm up for a pedant-off about definitions of oxidation and reduction, but it probably ought to go into another thread, certainly another forum, and possibly another site.
My assumption was that we were doing coin metals where the products did not turn into products that could evaporate over a very short time.
i think i ran into horn silver recently. This coin was very dark on outer layers, mineralization above that made it look like an encrusted bronze. I started digging through, it had a thin gold plate layer and underneath billon i think. Either billon is normally dark or this is horn silver. Very soft, hard to remove with taking more billon/silver away.