The design of this cover shows a series of radiating circles with various lengths of spoke. The innermost circle has 5 radiating spokes, only one of which extends to the edge. The second and third circles share 9 spokes reaching to the edge, and the fourth, fifth and sixth circles share 18 spokes, and the seventh and eighth share a total of 36 spokes, a New York City record!
This cover is the size that has been used in Central Park for watering valves.
This cover is on the 72nd St. Terrace Drive in Central Park near the Falconer, and is the only one of its kind I have encountered.