girldc's caps can tarnish very slightly if mishandled, but will not oxidize. also, he uses a super hard exotic alloy for the surface plating (there are multiple plating layers, however, which is how he gets the deep gloss).
there are no unplated caps there. the silver is his silver plating. it looks very similar to the original silver ironman. WOAH, he's doing an unplated cap? that's cool.
my understanding is that he uses an alloy that is basically a sterling silver for his production caps and pure silver for his master. sterling silver doesn't tarnish or oxidize permanently if treated properly. pure silver would actually be more problematic. the plated cap is the way to go if you plan on actually touching the cap. asura's sterling silver caps, for example, definitely showed wear after a while. even sterling silver is pretty soft. the point of plating is not just for discoloration but actually largely for hardness. it's a bit like finishing or polishing aluminum. you actually do it to get a hard layer of aluminum oxide (al2o3 aka alumina aka sapphire).
