Transponder Card? What is this...
 

Just took my 2010 V8 off the truck last night. This was with the paperwork. Can anyone tell me what this is? I don't remember seeing it with my 07.

The keyless entry works on that frequency, so I'd guess it's for that.

It's for Euro security system. If the car moves without the card, it is presumed stolen and the authorities are notified. You are supposed to keep the card on your person. It is a subscription service, as I understand it. Does not work in the USA.

The Aston part# is too blurred out for me to read, but here's the part numbers for the various markets:

4G43-37-10069 Module, RKE, 433 MHZ ROW/EURO
4G43-37-10070 Module, RKE, 315 MHZ Federal
4G43-37-10071 Module, RKE, 315 MHZ low power Japan

These may have been updated at some point, but those are the ones I'm seeing on Aston's Tech Info site.