From a period publication titled APARTMENTS OF THE BETTER CLASS
3 Flat using a interior design for what were obviously upscale residents. A good indication of this is the inclusion of a passenger elevator in a 3 storie walkup; a very rare perk even by todays standards. Then you have a driveway curb cut with access to both the main building and garage parking.
We have what has become the required servants room with its own private bath. Now open wood porches here; but a enclosed stairwell.This is not moderately sized unit.
I think the designers were anticipating adjacent future construction in that zero lot-line elements are present in the layout
You will note that the actual interior space is only two (2) levels. I wonder why they went went such a high parapet or were they planing on a third level. I think this was the case and they ran out of $$$$.
Boy have we all been there with a client at one time or another