Yes, a real stunner that has not gotten the accolades that is will deserved for doing Architecture with a Capital A… 
This facade is almost as detailed and opulent looking as the classical stone facade on the neighboring building.
It is good to see here at 200 Montaque Street an example of modern architecture that actually achieves the same rich visual effect as classical architecture; yet, without resorting to historicist decorative motifs.
Here is proof that Modern Architecture need not always be a boring glass box: though that, unfortunately, is the case MOST of the time… 
The main feature for me are those light colored vertical sections with the slight concave curves; they add so much visual richness to the facade.Those curved sections appear to me as if they are made of ‘solid’ stone: a big plus IMHO. I realize they may actually be thin metal hollow panels that are often used to achieve the look of ‘solidity’ - but those sections look solid to my eye, not hollow.
I am often disappointed by the look of the hollow metal panels frequently used on building facades; the hollow metal panels tend to look a bit flimsy IMHO. Here is a good example of hollow facade panels - NEW YORK | 1 Park Row | 305 FT | 23 FLOORS - #223 by Alemel
Or maybe they are hollow porcelain or whatever material - but HOLLOW. This example looks looks a bit less flimsy than when done with sheet metal.
I am going to guess those sections on the facade of 200 Montague are some sort of SOLD material: maybe not limestone - but SOLID. Both buildings look great - but 200 Montague is exceptional. A section-through shop drawing or photo would be needed to prove the question definively. 
Anyone care to wager?