Cherry Corp doubleshots are ABS plastic so they don't last all that long. I got a pretty used version once just to get some missing left shift key and after that it was all NIB donors for me.
It's a valid concern anytime you buy used Doubleshot keyboards - especially from a Point of Sales environment. The get REAL shiny.
Compare with the NIB doubleshot key below. Another tip - look for the oversized Tilde to confirm if doubleshot.
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(http://farm5.static.flickr.com/4151/4954924019_845a6274fd_z.jpg)
Stupid question, but can't you just sand blast them or something?