New York Mail and Newspaper Transportation Co.
This cover at the southwest corner of Park Avenue S at 39th St. is reminder of the network of underground pneumatic tubes that operated under the streets of New York from the end of the 19th century until 1953. Extending from the Old General Post Office south of City Hall to destinations in Brooklyn, Uptown Manhattan east and west (and perhaps even the Bronx!), the system was leased to the Post Office from 1897 to 1952. This cover was probably part of an important cross-town connection between the Grand Central Terminal Post Office and the new General Post Office building at Penn Station (c1912).
The simple basket weave design is similar to the cover's smaller, down-town brethren, but the cover is almost a foot widder (32.5 inches vrs. 21.5 inches) and also includes a foundry mark -- CLARK'S IRON FDY PHIL PA. The Clark name is seen often on Philadelphia lids, but rarely in New York City.
Maintainace access to underground pneumatic tubes.
This example is on Park Avenue South and 39th St. At least two other examples, one on Greene Street and one on Pearl St. are still extant (circa 2020) although how much of the underground infrastructure survives is unclear.