Went out to stare at the buttons...without taking one off and cutting it in half I can't tell if it's a 2 shot molded keycap or a clear part that's been painted and laser etched (which is the most common process now for backlit keyboards on laptops since it requires no special tooling)
I didn't feel like breaking my car so I didn't pry one off to be sure...but it's hard to tell if it was just a flaw in the molding like Joey suggests or something causing the paint layer to seperate like chemicals or heat.
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Current: '20 X5, '18 M3 ZCP
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