OK, cheating a bit here but Walter was so kind as to leave the source of his photo undiguised in the image.
With some wandering about it is the "Contraves" - by Slenzel/Heller
"The helicopter (which apparently never received an official designation) had a 6 meter twin-blade rotor driven by two pulsejets developed by Contraves."
It did fly, albeit tethered.
As I have other fires to tend for the next few days, if wout approves the answer, I'll make it OH.