The Schwarzenbach Buildings South, a 12-story loft building stretching across Park Avenue South from 31st to 32nd Streets, was constructed in 1912 and designed by Mulliken & Moeller. Built for Swiss-based silk importers Schwarzenbach, Huber & Co, who had previously been located on Broome Street since 1888. In the late 1920s, Schwarzenbach, Huber & Co. opened a salesroom on Seventh Avenue and moved their primary offices there in 1932. In 1946, they returned to this building, but left again in 1974, moving uptown on 6th Ave. The business closed in 1988.
The fanciful clock adorning the front entrance, known as the Silk Clock, was installed in 1926. It was designed by McKim, Mead & White, architects, and William Zorach, artist and manufactured by Seth Thomas Clock Co. and the Kunst Art Bronze Foundry. The terra cotta moths that flank the clock are the work of Marguerite Thompson Zorach. A New York Times account in that year wrote that a figure of Zoroaster, "the mastermind and doer of all things," is perched atop the clock. At his feet is a cocoon, and beyond sits a slave representing the "primitive forces and instincts of man." Hourly, Zoroaster waves his wand, and the slave promptly swings a hammer against the cocoon, triggering the emergence of the 'Queen of Silk', tulip in her hand, and not until the hour has ceased striking does she disappear."