This is the power supply unit, mounted upside down from the orientation found on the Master Compact. Not terribly interesting in itself, although there is a surprise in store...

This legend appears on the side of the power supply unit. It is the same as a Master Compact PSU although not all Compact power supplies carry this legend. The Master Compact was obviously known by Acorn as the "Baby B" although whether the "B" relates to BBC Model "B" or Project "B" (which is the development name of the Master 64, as it then was) is an interesting discussion point. "Monitor Stand" was evidently the name for the Master Compact disc drive/power supply box.