Peyton to the Broncos, Tebow to the Jets and Peyton has a Unknown Extra Signature?

The NFL world was shaken when the Denver Broncos signed Peyton Manning for five years.  This caused a trade with the New York Jets sending Tim Tebow to go to the Jets.  This was a big surprise for me as I expected him to go to a different team.

Whilst I looked into the trade I decided to look at their Adrenalyn cards from booth series'.  I managed to find a Extra Signature of Peyton Manning on Panini's website.  I've tried looking everywhere to find out how to get it but I have not managed to find anything.  If you look at it it says "ESPM" where the card number usually is.  Below is a pile of both their Adrenalyn Cards besides Peyton Manning's series 2 base and ultimate cards.  If you notice, both Tebow and Manning are the only two NFL Adrenalyn XL players to have a special extra signature.

Base, Ultimate and Pre-Production 

The unknown Extra Signature (I want one)

Base RC, Panini 50th anniversary RC and Base 

The Tebow Extra Signature