Explanation
What appears to be an innocent packet of business cards and envelopes is actually a highly precision device for gathering information. The magician removes one of his business cards, turns it over and places it on the top envelope on the backside of the pack.  But underneath this envelope, is a magnetic strip that reacts with the ink in the pen when the spectator signs the card. When the magician removes the envelope, it exposes the magnetic pad to the magician.  He can now clearly see what the spectator has written.
Precision Gaffed Pen
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Signing Back of the Business Card
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Envelope Being Removed
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Image is Now Revealed to the Magician
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