Original Apple, fully tested Microphone, Rev. B for the Power Macintosh/Performa 52/5300/5400/5500 Series.
Apple introduced updated versions of the 5200 (excluding 5260 & 5280) and 5300 series several months after introduction referred to as Rev. B with some revised parts that are not backward-compatible.To determine the version you are servicing, remove the front bezel and note if the speakers are part of the front bezel (Rev A) or attached to the sides of the metal chassis (Rev B).