C'mon the second T is covered with sand
In 1928, after a few years of studies, and more importantly, after Newark Airport was designated as the New York Regional Air Mail Center by the Post Office, New York City started to build Floyd Bennett Field. The lead agency was the Department of Docks -- the interlocked DD in the center.
The department was renamed the Department of Marine and Aviation in 1942 for its efforts.
The linked D D is a strong center for this variation on the wheel and spoke design. Note the tapering spokes coming from the edge.
The ring of vents hints that this is a sewer cover.
There are very few Department of Docks covers still to be seen in the city, all apparently at Floyd Bennett Field. But keep your eyes peeled!