The locked door was certainly new, once. It may well have led into a 3-bedroom house. It is not difficult to imagine a 3-bedroom house with a balcony. There are several early 20th century houses nearby, with balconies overlooking the street. This could have been just one other such.
But really, the brick wall behind the door and the window pane makes a mockery of the door itself. And a ghastly breach of security, one panel of the door has been broken up, providing easy access to the brick wall behind!