Most of what I found about sharkskin being used as armor was from the bronz age. I found a few articles written about shark skin and armor but they only spoke about it for a couple of sentences, mostly the armor of choice then was rhinoseros hide. The information I received about the sharkskin and armor came from a guy in my Kung FU class (which was along time ago) who had bought some antique weapons and armor (illegal or legal I dont know) which came from china ming dynasty I believe but not sure. Anyhow from what I found from varios sites is that sharkskin doesnt last long in hot climates so there are not many samples around to day. Also shark skin was used more for the palms of gloves and the hilts of swords for extra grip.