The stock radiator for the 47-53 was a Harrison Radiator ( a division of General Motors).
They had brass alloy tops. In the Korean War years, ca1951 , brass was critical for the war effort and Chevy did briefly uses a ferrous alloy radiator top. It rusted quickly and needed to be dealer replaced.
Regardless both versions of the radiator had a black coating to prevent corrosion.
I believe the "black paint" could have been a carbon black and shellac-like mixture, not what we commonly think today as "paint",but black paint-like none the less ...
