Prima Satin Chrome Scroll Knocker SCP20 Prima Satin Chrome Scroll Knocker SCP20 5.25 inches x 1.25 inch.  (145mm x 32mm) Bolt Centres 4.25 inch.  (110mm) Solid Brass Architectural Ironmongery. This is hand polished and finished in Satin Chrome.  A collection of door knockers. door knobs. letter plates. and bell pushes. Also window fasteners. window stays. pull handles and lever handles. The Prima Satin Chrome Collection offers quality and elegance that cannot fail to enhance any property or style of decor.  There is also a large variety of electrical accessories to match