Case hardening techniques..what else is out there.

I know that Sinn tegiments some of their bezels and cases. Damasko ice hardens their cases. I have also seen that Ocean7/AirNautic has a model whose case is ice hardened. Who else does this type of thing? The reason I ask is that I have a Damasko that seems to very scratch resistant. Worn it a lot over several months and there is not a mark on it. Are there any others using these methods or others to harden a case. I'm not really interested in DLC as it is just a coating I believe. Would like to see what else is available with this type treatment and hear about anyones experiences with them.

It amazes me that they have not yet figured out how to make stainless steel black all the way through...

The Bremont diver also uses a hardened steak.