There's a parallel topic going on on NBR wagon grey, in which @Penlan has posted a couple of scans of photos that are relevant to this discussion:   For convenience, I'm copying his second image here:     The 4-plank wagon in the foreground has very worn paint on its woodwork. The ironwork looks black. Is that because the metal components were given a coat of black before the wagon was assembled, then overpainted grey, but the grey has worn away?   The q