Is this oxidation or something else - 1944 Omega 30T2

[thor447]

I was curious about what this corrosion actually is on an Omega 30T2 dating to 1944.  Nearly all of it cleaned off with some pegwood and a little effort, but I'm curious if this is oxidation or some other type of corrosion.  This is in a 14k rose gold case.  In my research on this movement and the history of Omega finishing on gold watches, this uses an earlier (and unstable according to some) rose gold plating with the following alloys:   85-90% copper, 10% silver and 3% gold, 3% zinc.  Later on (years after this watch was made) they changed their rose gold plating to 10-20% copper, 80-90% gold, 3% zinc (data provided by a user on OmegaForums.net who published a book on vintage Omegas and had a SEM analysis done on the parts to get plating data).   I'm thinking that with the high copper content on the original style plating that what I'm seeing is oxidation, but I find it strange that it mostly resides on the edge of the main plate, bridges, etc.  Can someone shed some light on this, or does this look more like regular corrosion from moisture over time?  Outside of the stem, none of the non-plated parts in the watch had much of anything in the way of rust.

 

Edited January 12 by thor447