Are you sure about that - because that is a very obvious Mercedes-Benz - or Daimler-Benz three pointer on the tail...complete with shadowing in the right place, etc...
Auxtank is always prepared to be proved wrong...
Was this like - a one off? Noted; the lack of a King Post - did the aircraft fold up on the first flight and was never seen flying again?
Would anyone have heard of this - if they hadn't read a particular book - of which only 200 copies were printed?