Correct me if I am wrong but chrome plating metal and 'chrome' plating plastic are two completely different processes....Doc chop sent all his stuff out for plating.. actually at the time he did the big batch a lot of people lost their frames. I've seen and owned some of the plating chops company did. It was awful as most of them had the chrome fail within a few wears.
Plastic has a thin layer of metalisation applied under a vacuum - usually aluminium? Hence the bond not being as strong as the chemical process of chrome plating metal.
Fortunately, my pair still has the coating perfectly intact...