Brand New 3 bolt...air or smog pump pulley for the GM vehicles from 72-85.. when many went to serpentine belts.
Note .. on RHD cars.. (in Australia).. these were often swapped for something smaller if in the way of the RH Mounted Steering box... but otherwise. .at 5.9 inches.. this is it.
Stamping AD, BDC, FAB, MU