This looks very similar to the model for 655 Madison. Maybe with some luck, that will be a Stern too. The demand for an 1,100 foot+ Neoclassical, limestone, Stern on Madison would be unparalleled and would far exceed that for a glass tower.
Moreover, the architect could easily incorporate large, double-height bay windows framed by copper and limestone (e.g., like the ones on the southeast corner of the facade on 520 Park) on the ten or so lower floors of office space. For that matter, 520 Fifth has at least ten stories of office space, notwithstanding its classic, stone facade.
Perhaps, Beyer is just the A.o.R., but even apart from that possibility, that firm has designed Stern-style towers.
655 Madison