That looks like the QSI setup before they went to the two-board setup and produced the MTH PS/1.
I don't believe that's the DD Equalizer. I'm holding an Equalizer board now, and it doesn't' look like any of those boards.
The Equalizer only worked with MTH PS/1 top boards, the three board stack would not work with it in any case.
This is from the Equalizer manual, my board looks exactly like this picture.