I am not sure if Canon had a uniform system for making black paint cameras. I have seen pictures of several black paint Canon rangefinders that appear to have a substance like nickel (somewhat silvery, but not as bright as chrome) below the black paint, with deeper scratches showing brass. I have also seen pictures of other black paint cameras that appear to have a layer of paint serving as an undercoating for the final layer. And I have seen pictures of black paint cameras that appear to show only brass beneath the paint. Kevin Li has some detailed pictures of black paint Canon rangefinders that he for sale on his website.