USB Wi-Fi adapter + external antenna?

Hey! I've got this wireless gear here: http://www.edimax.com/en/produce_det...id=1&pl2_id=44
But I’m stuck on this antenna—no clue what its actual value is or what the dB rating is... anyone able to help a guy out?
Here's a pic: http://i47.tinypic.com/2v0iq69.jpg

P.S. I'm actually looking to sell it—just trying to figure out what kind of cash I can get for it

It really depends on how old it is and if there’s still a warranty left on it, but honestly... 80-$33 ☕

the antenna is brand new... plus this card is worth its weight in gold—edit: $33