1937-39, Alan B. Mills.
Federal Seaboard Terra Cotta Corporation. Extruded terra cotta on the facade and interior. Post office. (Source: "Terra-Cotta Skyline", by Susan Tunick).

New York may have the most impressive collection of post offices in the world -- off-hand, we can think of the former Cunard Line headquarters with its incredible interior, and then behind "Horrible New" Penn Station, there is the massive Farley Post Office which the Municipal Art Society (and others) want to recreate as the reincarnation of the "Late Great" Penn Station.

To which we now add our terra-cotta treasure above -- it does have a very nice interior with large artworks, including a terra-cotta sculpture. The exterior is entirely clad in glazed terra cotta of "rosy buff, oxblood, green, and black with areas surrounding the chamfered[*] corner entrance highlighted in silver metallic lusters [2-jpg; framing a molded glass block window]." (Source: "Terra-Cotta Skyline, p. 112)

3-jpg shows rosy buffish grout used between the rosy buff pieces, and blackish between the blacks. Also, what happens if the glaze spalls** -- it reveals the buff-colored claybody, surprisingly rough-textured, like when you pull the crust off a piece of bread.

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*"Chamfered" means rather than the corner coming to a point, it has been shaved off/smoothed out, as one might round off the corners of picnic table to avoid getting splinters.

**"Spalling" is when the material deteriorates over time and starts to crumble.