This photo gallery shows three pairs of early 908 Magnesium brake calipers which the Porsche Werks department initially made available as prototypes. The 908 Magnesium brake calipers were purposely used in the "hill climb" 908 cars being much lighter than the more common Aluminum type (if you can refer to an Aluminum 908 caliper as "common").

Rumor has it that the thermal characteristics of the Magnesium calipers tend to allow them to distort more so than the Aluminum alloy counterpart. These Magnesium 908/3 racing calipers today are very rare parts indeed...