They are very similar to 914-6, but with some important distinctions.
914-4
Black paint
Smaller diameter
914-6
Gold in color. Probably zinc with yellow chromate.
Diameter ~308mm
The radius of the outside bend is larger on the 914-6, giving it a slightly bigger diameter. A 914-4 brake plate will stack / fit inside the 914-6 plate, but not the reverse.