Hello Benedikt,
it's a little bit curious.
The serial no. says it's a Rolleiflex Automat third model (805.000 - 1.099.999) built from march 1939 till september 1949, all about 38.600 pieces.
Since 1946 with a Zeiss Opton Tessar taking lens.
Bayonet size I for both lenses. (Prochnow, Rollei Report 1)
Afalter says serial no. 805.000 - 927.999, Tessar with bay. I on both lenses is a Rolleiflex Standard (new) K4-640 Rollei internal name.
The Rolleiflex before this ones without a taking lens bayonet (instead 28,5 mm push on) is a Rolleiflex Automat (RF III A), serial no. 568.516 - 805.000, august 1937 til january 1939, without the red window.
Does is help??
Greetings from Germany
Chris