On the other hand, if he knows the method of the Mystery Box, he should also know it doesn't work the way he described. The performer has to show the card in the box, no it's not examinable beforehand, and the performer then dumps the "card" into his hand (with some sleight of hand) as he lets the Mystery Box do what it's famous for which is to hide the gaff in plain sight so the box can be (casually) shown empty afterward.
In other words:
The Mystery box is preloaded with a fake
The performer handles the box at all times
Yes, they can lift the lid but you do all the rest of the work
The dummy card in the box is *not* the actual chosen card
The card has to be dumped into the performer's hand, not the spectator's
The box can be shown to be empty and can withstand some light examination
This last point is the strongest selling point for magicians who like overpriced mechanical gadgets, but is also the worst reason to buy the box. The heat should never be on the box in the first place. Flash the insides as empty and PUT IT AWAY.
I can do all the above (except for showing the container empty, but it's really not a big deal as the attention is on the card) with just about any ungaffed box that will hold a folded card.
BTW, a Lippencott box uses a totally different method. It's usually a locked box, you can show it's empty before locking it, or just bring it out already closed and tell them there's something in there (when there really isn't). You then have to have some choreographed justification for handling the box after the item (usually a ring, but if a folded card fits it works too) is vanished to allow you to insert the item into the "locked" box. After that, they can unlock the box themselves and remove the contents themselves.
That's kinda' where I was headed with with my comments. I think it is a bit pricey for what you get and I think there are several Ring boxes(lippincott style) that can be purchased much cheaper and are a bit more versatile.