That's a good question. The front of the building is actually a facade “false front”, and you can see the original brickwork behind the windows. Norm Gagnon pointed that out to me when after I went to see it, but I would never have noticed it otherwise.
This also probably supports Ectoman's statement that it was narrowed to allow wider streets. If they narrowed it, the brickwork would no longer be consistent, so they'd have to design a new front and side. You'll notice how the other side of the building (the side not facing the street) isn't consistent in design with the other sides.
Since it's a public building there must be a record in a city archive somewhere of its history. Maybe someone in NYC can check out the public libraries for info or something.