I have seen a few 71 200 SS MK2 with black pipes beneath the chrome heat guards. Most notably is the one that Carlos Santana had restored -
https://www.motorcycleclassics.com/classic-japanese-motorcycles/classic-bridgestone-motorcycles/1971-bridgestone-mach-ii-ss-zmwz15jazhur. When I initially saw his restoration I liked the black pipe look but thought it was probably not a stock representation but a personal preference however, if you follow that url there is a photo of that bike pre-restoration and the pipes are black there. Does anyone know for certain the history of those black pipes? Seems like a lot of chrome went away when Rockford took over putting the bikes together and BS was out of the picture. Thanks