I just bought one my self about 3 weeks ago, so far I love it, the X15-TN admittedly doesn't hold and edge as well as any of my other knives("lowest" other steel I own is 154cm), but is more than adequate for my EDC needs at work and sit very easy to maintain on my sharpmaker. If I had to guess it's probably around 440C or maybe AUS-8. I mainly bought it for the extra corrosion resistant the steel and G10. I work with a lot of a lot of bleach ranging from 10% to 50% concentration, more than enough to ruin any steel, so every little bit helps. More generally it is a limited edition for Benchmade's Law Enforcement buyers Program I believe, hence the little Sheriff's style star on the clip.