These are custom tin cobalt plated machine screws made using type 316 stainless steel, designated by a dot on the head of each screw.  Like the other custom tin cobalt chrome plated screws, these machine screws are manufactured overseas and supplied to our long time customer on a revolving blanket purchase order basis.  The tin cobalt chrome plating is done in a barrel plate format for improved cost efficiency while still producing a very attractive cosmetic finish.  Tin cobalt finish typically provides a slightly duller chrome finish than the traditional hexavalent chromium plating.  All the custom tin cobalt plated parts we supply are electroplated with a bright nickel under-plate for improved longevity and appearance.