Ironstone was the former Spyderco factory outlet (SFO) before they became known as that. Originally operating out of Colorado, the store eventually moved to Hawaii where business continued for about three years. It closed down in year 2ooo. There were a few knives only sold through them which is listed as Ironstone exclusives. Most notably the CFIFP. The C03 Hunter with the C13 blade is sometimes referred to as the Ironstone hunter, and was indeed Exclusive for the Ironstone but made available to dealers as well when Ironstone closed.  
- http://www.spyderco.com/forums/showthread.php?t=16438&highlight=Ironstone Link to some info on the Spyderco forums
- The rest of the information not in the Spyderco forums thread is gathered from posts made by Sal on Bladeforums.