Mystery Solved!

Thanks to Colleen, we no longer have to lie awake, fretting and tossing through the night, wondering from whence and why this lovely architecture.    Colleen wrote:

According to my AIA Guide to New York City (4th Edition) this this the Fred F. French Company Building, constructed in 1927. H. Douglas Ives and Sloan and Robertson (architect): "The headquarters of the former design-builder company has strange multicolored faience at the upper-floor setbacks and a well-preserved ornate lobby. From the days when even the greediest developer owed serious and intricate architectural detail and materials to the tenant and public."

You can read more about the Fred F. French building here. 

** Update:  More info from Colleen!

The address is 551 5th Avenue.

It was designated an NYC landmark in 1986.  According to my Guide to NYC
Landmarks (3rd Edition):

"The prominent Fred F. French real estate firm erected this skyscraper
with massed setbacks (? how setbacks are not "massed" I do not know.) for
its corporate headquarters and for rental income.  The use of detail
inspired by ancient Mesopotamian art is an indication of the exotic
historicism that was prevalent during the 1920s.  The exotic influence is
especially evident at the base, where the bronze entrances and storefronts
are embellished with mythological figures and Near Eastern ornament, and
at the crown, with its vivid poly-chromatic terra-cotta decoration.

INTERIOR:  The ornamental motifs in the magnificent lobby pick up exterior
design elements.  The lobby has a vaulted ceiling, bronze doors, and other
elaborate Near Eastern features."