Nice score there. It is a Generation 2 Howling Rat 4-tooth Razorback or Ridgeback. They were made available at Blade West '06 and the Busse Knob Creek Liliputianganzaaa Fall '06. There are 4 variations of this style that were released. At least one had 3 teeth, there are quite a few 4 and 5-tooth versions, and one 6-tooth. I don't think anyone knows the total amount of 4 and 5-tooth versions that are out there, but they are somewhat rare. They were all finished in the Swamp Rat Custom Shop and there is even quite a bit of variation in the way the spine and teeth were ground. I have seen the variation mostly in the 4-tooth versions. It is mainly in the lenght of the grind and where it begins near the tip. All these models sold originally for $158.95. You probably won't find any for that price now, with most that I have seen ranging from $200-$250 for mint versions.
Just for kicks, I know that the 3-tooth version is a bit of a mystery and its location is currently unknown unless it's resurfaced recently. The 6-tooth is in a private collection.
For good info on releases and original prices see this sticky made by Paddling_man. It's at the top of the Swamp Rat sub-forum page.
http://www.bladeforums.com/forums/showthread.php?t=515896
Also for more Rat info go to:
www.swampshack.com