Does anyone know how Stowa achieves blue screws on the movements that feature them? I recently received a Partitio handwinding with a display back. It has the SW215-1 movement and features some rather nice blued screws. Close inspection shows that the slots of those screws are not blue but polished -- does this indicate that the screws were chemically blued vs heat blued? Is there some other process used? This doesn't impact my enjoyment of the watch at all; I'm just curious to know how my watch was made.