The Steel of the Rydlin region is a stronger and harder steel than normally available. The steel has a slight blue sheen to it. This comes from additional materials the locals add to their steel recipe and the minerals found with the local iron. The steel will have a slight Damascene pattern, which is often enhanced by the "proper" techniques the smiths of this region use.
Items made of it are more durable than normal and will hold a hard edge (and harder to sharpen). Assign bonuses as appropriate for your system. Rydlin smith produced superior materials as well, so they get expert, if not master craft bonuses.
Science Note: Molybdenum and Vanadium added to steel produces a blueing of the metal and great strength. It is used by custom knife makers today to create exceptional blades.