Okay, so this isn't a perfect trick. But it's a wonderful idea, and can be customized as you see
fit.
There are multiple outs here, one of which is very strong, two of which are somewhat weak,
and two of which are strong but a bit tricky. (I'm referring to the card box.)
An easy
enhancement to make the trick stronger: have a single examinable card in the card box, and another
card reversed in the pack. You can then dump out a single examinable card from the box (strong and
easy) or spread the deck for a strong reveal.
There are many other possibilities as well. "The
Fine Print" by Jay Sankey has an Ace of Spades with tiny print saying "I know you will pick the
Queen of Hearts!", which could easily be placed at the top of the deck and even forced if necessary.
"The Big Finish" has a powerful whammy where four cards form a jumbo King of Hearts.
I have
an "Astor Card Frame" gimmick (which is fantastic, btw) in which a Jack of Hearts appears, but can
transform into any card on the way out (for instance, the 10 of hearts, to make that revelation
stronger.)
Possibilities are endless. You could use "Monkey in the Middle" to produce their
selected card in a sandwich, etc. If each reveal is equally strong, you won't be disappointed that
they picked a particular selection.
Bravo, Oliver, for a wonderful idea at a great price, and
for inspiring our creativity.
You are a gift to the magic community!