Dragonscale is relatively new.. it's basically just a mutation of the scales - originally made for thicker, harder scales for fighting. They are becoming wide spread and popular.. yours is a "full mask" dragonscale meaning it covers his head/face.
Basically, just thicker scales.
Other traits are just the body, or there is a line going from mouth to top of the head void of these scales.. also could have a pattern that seems to be checkered type.
I personally love them in pictures, but not in life as much.. surprising since I have 3 or 4 dragonscales lol.
Here are a few of mine as reference..