Engraved on a black plastic label at the front is "ACCUMULATOR." "INDICATOR PANEL MOD II" and "M.I.T. DIGITAL COMPUTER LAB" are both printed in white at the top of the panel. There are 16 red indicator lights and 16 white indicator lights. At the back is an add on wire wrapped integrated circuit board in attached to the inside. It is attached to a multi colored ribbon cable. A label attached to the unit reads "Whirlwind Stack 3N."