It is sapphire with AR coat. It's OK, though you know this AR coat is only so good. You have to send it out for double coat if you really want some good AR.
Edit: I just learned that Davidsen sells his watches with WR30m. Now to me this means I can wash my hands or walk in the rain without worrying about small splashes but that I cannot take it under water at all....
I seriously doubt he services and regulates them at the price he sells. Those are services I believe you would need to get from a watchmaker. Personally, I don't see much use for servicing or regulating a new movement. I will wear it for a while and see if it is keeping good time. If not, I will have it worked on. (I mean sure, it's great if you can get this service included in a new watch for a reasonable price...)
I don't plan to wear any of these in the water so I don't feel like paying to have them pressure tested.