Hitachi Apple Badged Drive Label With Incorrect Model Number

Just recently we received a failed HTS543232L9SA0 from a Macbook Pro. When we carried out the initial diagnosis we noticed that the drive capacity was 160GB and not 320GB as the model number suggests. The Model number should have read HTS543216L9SA0. This particular hard drive has a black label which is different than most Hitachi drive labels of the same type. When we opened the drive in our clean room we found that the drive only had two heads compared to a 320GB which has four. When the drive is attached to our hardware or a PC it identifies correctly as a HTS543216L9SA0.