009 is the last three numbers of the zip code for Carlsbad, Ca, where SC is located. It is my understanding he did this to pay homage to png, because early png equipment had the full address on the club. As far as how it differs from other models...

Most, maybe all, 009s are Newport heads, or variants there of. They are hand crafted, hand stamped and will not have the same characteristics as off the rack models. The most obvious difference is on the sole, where is will never have the off the rack designs. 009s are pretty much tour issue. I think all 009s are made of carbon steal, not stainless. The Tour Rat is SCs latest tour issue Newport, which uses the interchangeable weights, deep milling and inserts, if you include the Super Rat. Different materials, different look and different feel. 009s can be a little flashier with the various stamps where Tour Rats tend to be more uniform. Both are really sick sticks.

Hope this helps, more importantly I hope it's all correct!

Yes, the 009 does stand for the Carlsbad zipcode, but the head is made from stainless steel. 

Eric and Cathi,  thanks for the info as well as your help!