I had the opportunity to talk to Sal at the New York show this weekend. He said that the locking liner used to be made of steel, but they've since switched to titanium. Mine is number 690, and the liner is steel. I played with a current production model at the show, and you can really tell the difference, because the Ti liner is more "sticky" when releasing the lock. BTW, Sal is a great guy to talk to. He's on top of everything Spyderco, and didn't miss a beat. Hope this helps!