I wonder if anyone know what's the different between these two sigma lens. APO 50-150mm F2.8 EX DC HSM APO 50-150mm F2.8 II EX DC HSM what's the different for one with II? I got an offer for the one without "II".. the guy said it comes with 10years warranty, but he doesnt has the receipt, just a blank warranty card. would i be able to claim the warranty if there isnt a proof of purchase. Thank you.