Early DPW in Central Park
There have been several reincarnations of the Department of Public Works in New York over the past century and a half, and this cover seems to be pointing back to the 1870's edition. There is no date on the cover, but it is almost an exact duplicate of a lonely cover found on upper Broadway with the inscription "CAD" Croton Aqueduct Department. By 1870 the CAD was responsible not only for the aqueduct, but for the distribution of water in Manhattan. This function was taken over by the newly formed DPW, and as in many bureaucratic switches the designs used by the previous department were updated with a change in lettering, not in overall design. In this case the same font family was used (compare the D's.) It is certainly one of the oldest manhole covers in Central Park and the city.
A wide spaced diamond grid with raised lines is the background for a rectangular badge with three letters, with no periods. The cover is exactly the same size as the CAD cover found on Broadway (19.5 inches) and differs only in having one pry hole filled, and having a small drilled vent hole (above the D.)
Post reservoir water distribution
This cover is the only one of it's kind I have seen. It is located a little north of the Disco Skaters in Central Park.