DESIGN:
The Neenah Foundry is one of the largest man-hole cover manufacturers in the US, but, like the BWS, has only a limited presence on the streets of New York. It is also one of the few foundries to have a video about the design history of the firms manhole covers! Neenah Video . This cover is their Cope B "Waffle" design, made since 1934.
UTILITY:
This cover probably allows access to valves along the Third Tunnel adjusting water levels to lower Manhattan and Queens.
RANGE:
This cover is on the 79th St. Transverse of Central Park, just east of the East Drive bridge and is unique as far as I can tell.