They are called Target CDs for their unique painted label side surface that resembled a targeting reticule with the markings at 3, 6, 9 and 12 o'clock respectively.
Many collectors and music 'purists' prefer these original pressings for their 'flat' transfers of the original masters of the recording and not the re-mastered CDs of the last 15-20 years that have been part of the 'loudness wars' which adversely affects the dynamic range of the original recording by making it 'louder'. This creates loss in the high and low frequency response of the recording.
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Example of a target cd: