Just picked up a Canon 100mm Macro and having a little problem finding anything out about it. I believe it's a older model of the 100mm 2.8 Macro because it has a metal body. Is that the same as the USM? I'm guessing not, but can't seem to find the sample thread for the older, if there is one for the older model. Also, do they make a hood for it and do I really need it since the lens sits inside a way back? Any help in the right direction would be greatly appreciated. Thanks in advance!