It is a sketch of the BMW PT 2000 from 1966 by Manfred Rennen
One more point for you!
There may be some confusions with the Brabham-chassis. The Apfelbeck engine has been tested 1966 in a F1-Brabham-chassis. It's not clear, if that was a BT 7 or BT 11...
If the PT 2000 should have been based on a Brabham-chassis, only BT 8 would have been the choice. But there is no proof of that anywhere.