Cobalt Special

Cobalt Special is a steel made by Takefu and consists of:

Carbon	Chromium	Cobalt	Copper	Manganese	Molybdenium	Nickel	Nitrogen	Phosphorus	Silicon	Sulfur	Tungsten	Vanadium
0.95-1.15	15.00-17.00	2.00-3.00	/	0.30-0.50	1.00-2.00	0.25	/	0.03	0.60-0.70	0.01	0.20-0.30	0.20-0.30

Some information from Michael Janich in a thread on Spyderco website:

The most notable element, as the name implies, is cobalt. For comparison, standard VG-10 contains 1.30-1.50% cobalt, N690Co contains 1.50%, and CPM-S110V contains 2.5%. At 2.00-3.00% cobalt, Cobalt Special will offer more of the qualities this alloy provides, specifically increases in strength and hardness and the ability to quench at higher temperatures. Cobalt also acts as a catalyst to intensify the benefits of other alloys.

As far as stain resistance, at 15.00-17.00% chromium, it is well above the threshold of a stainless steel and contains more chromium than VG-10's 14.50-15.50%.

Part of the challenge of providing information on this steel is that very little information is available on it in English. Takefu's own web site does not include it in their list of steels.