All I've got so far is that the braille should be kept simple, just to ID the Yubikeys one from another.
This would allow a quick ID of which Yubikey is OTP versus the second or third Yubikeys that have been password programmed by the user.
But they'd also need to ID one user's Yubikey from other user's Yubikey.
So the second row would have to be personalized, or serialized for clarity.
I can see this concept now makes it fairly specialized and that it would cost more per Yubikey.
But this would give you a head start and something to open dialogues with, if/when Yubico should encounter such a question...
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Reference:
http://en.wikipedia.org/wiki/Braille