I had a pair of Accoustats that were identical to the ones in this picture.
They did not have the solid wood cabinet underneath.
The speakers were called "Accoustat Model X". Roman numeral ten, IIRC.
They originally had a vacuum tube power supply. The vacuum tube PS had been removed from mine. I installed Hafler SS power supplies from a pair of Accoustats IIs. It was enough to drive the three panels.
I've never heard of a Model 3 Accoustat.
The Xs were really nice sounding. The Quad ESLs were much better. Several Martin Logan models also made a superior sound than my Xs. Of course mine were patch work. I gave them away.