For the record, I like Jon Allen's Destination Box and think it's yet another interesting and valuable variant on this theme.
With all due respect, I really think that in public discussions of the historical record, one could stand to be a bit more circumspect before making statements like "I swear Persi told me about the use of a card case and the card attached via a thread was his." No flame wars desired or intended, but a statement I think worthy of mention. Caution is a benefit to ALL parties concerned -- the spoken of, the spoken to, and the speaking.
In other matters ... ah, yes, the late Peter Kane's Card in Ring Box -- which incorporates a very deceptive idea. (I saw Bruce Cervon perform this very effectively, ages ago at the Castle.) I recall first reading this idea years ago in one of his "Card Session" manuscripts. Gary Plants makes a cleverly gaffed version that allows you to show both sides of the box (whether this is a necessity is arguable, but the gaff is superbly made, as with all Gary's work): http://home.houston.rr.com/mylist/index.html