This is an excellent guess, Roger, but not correct. If any photo of the Rathbones' Hannover home in Heinrichstr. 27a (2nd floor, rear side), exists it won't be a post-WWII photo as the house was destroyed in the war. This is the building #27 nowadays:
The opposite houses are still original Wilhelminian style, and this is the house exactly opposite to #27:
Hint #1: The residents of the house in my question moved away in 1865. (BTW, did you notice the house was exposed to the Polarwirbel?)