Was Albrecht Mantzel involved?
Please ignore the above question. Whilst investigating further into the world of DKW tuners, I found the answer. It's the Hey Mk.1, built by Dr. Theophil Hey using what he called an Elva body/chassis (so it's probably an Elva frame with an Ashley shell), and a self-tuned DKW F12 engine. The year is a bit vague - he built it during his days as a medical student, in the early 1960s.