West 91st Street Marine Heroes Tablet
The Parks Department website indicates that this monument is a granite replacement for a bronze plaque originally mounted in concrete and dedicated around 1950. The monument seems to have outlasted the organization that commissioned it since I couldn't find anything about the Marine Corps Fathers' Association of New York on the web. (reference)
IN MEMORY OF
OUR MARINE HEROES
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MARINE CORPS FATHERS' ASS'N.
OF NEW YORK