Mr Night,
if you have an old old old original Tigershark, from the SOG Santa Monica days, my best guess is that the steel is SK-5 carbon steel. And I'll guess too that there are no serrations on the blade, another indicator of SK-5.
I'm very fortunate to have an SK-5 Tigershark and I really like the SK-5 steel. It is very easy to sharpen, and believe me, I am hugely sharpening-challenged, yet I am able to put razory hair-popping sharp onto the edge. And the sharp-retention edge holding is very good.
What I also like about the Tigershark is the weight. I have whacked and hacked at 4" diameter tree branches and they were no match. Plus the weight of the Tigershark made me think it was an ax, there was no handshock at all while easily cutting these branches.
Cheers,
Carl