Don't know if PBT changes much, but it would probably look like a PLU ML-87 seen here: http://geekhack.org/showpost.php?p=277467&postcount=7
I found this pic in a Poker review by Sixty at deskthority.netShow Image(http://i.imgur.com/kFoKn.jpg)
That should be a Cherry Corp PBT key. Those are really thick, so a thinner white one(like those you can get from imsto) should be more see-through.
Source: http://deskthority.net/viewtopic.php?f=4&t=125
That's a thin Signature Plastic ABS key.
Hey, don't mess with my photographic memory! :)
http://geekhack.org/showpost.php?p=295118&postcount=30 (http://geekhack.org/showpost.php?p=295118&postcount=30)