Bear,
Some of the things that were unique about the Zero Tolerance(ZT) knives, were they were 3/16" thick INFI, rather than the normal 1/4".
They also had unique grinds, they had the satin finish and they were limited to 400 pieces for the NO, SH-e, and BM-e, and 100 pieces for the ZT SJ. They are no longer available from the Busse Shop however, they do come up on the secondary market.