Simple idea, but as you might guess, this is surprisingly entertaining to lay audiences. '
A card is chosen, and you claim that your pen is a mind reading pen. You show a message in a window on it's barrel -- "think of your card". As the spectator thinks of her card, you click the pen plunger a few times. With each click, the window message changes, and eventually hones in on the correct card.
It is the same card every time, so no good for repeat audiences, but a lot of fun for those watching it for the first time.
As you can see in one of the photos, this prop was put out by Danny Archer in 1997, twenty-five years ago. I got some of these in a purchase lot of ex-dealer inventory, and as you would expect, the pen ink had long dried out in every one of them. BUT I have replaced the ink cartridge in the pen, so it writes just like new.
(Hard to find this prop nowadays, but if you do find it elsewhere, and buy it elsewhere... well, be prepared to get a pen that does not write. And maybe you will find the only pen refill currently available that will fit in this special pen... well, it fits after you do a little bit of internal modifications to the spring, etc. You get the idea. If you want the pen to write, as well as read minds, you should buy it here! The one I send you will write!)
New and unused, but original (old, dried out) ink cartridge has been replaced so that the pen still writes. Complete with original instructions.