Apologies for late response to the thread. Drawing clearly lifted from my book.
It dates to June 1943 and was almost certainly a 'private' design by Reder, although it's clearly designed to move beyond the preceived weakness of the Fa 330, its unpowered motorisation. It is not clear if it was shown to Flettner, his then employer, who was in any case struggling to meet the RLM orders he had in hand. Reder moved on from Flettner in November 1943 to Ruhrstahl AG where he worked on the X-4 air-to-air missile.
The drawing turned up in the Nachlass his daughter deposited with the Deutsches Museum following his death.