very interesting.

On close examination of my 10x15 I can now tell you that your "46" is not the Serial number, but an internal number.
Because my completely regular Serial cam has "29" embossed on the end of the base plate as yours (have overlooked it until now) an on the bottom of the lans stand. So this seeems to be In-factory Standard to get the right fitted parts together. The beabies were really handmade, the 1937 Katalog has some production photos that Show the craftmanship. It was no mass production...

So your camera has to have a Serial number elswehere or it has None, whicht would indicate a prototype that was not intended for sale...???
Maybe an american soldier took it from the factory in 1945 when the conquered munich. but that is speculation!!!!

the lens does not help us, as it a 1930 Tessar with 135mm, so not original to this camera.
Maybe the shutter, ist Serial number is on the side of the shutter below the aperture Lever...