The Pulitzer Mansion on East 73rd St. is not quite as posh as it once was, and they've let their coal hole cover get downright tatty, the strong design by Tice and Jacobs still gives it an air of respectability.
The hexagonal studs around rounded hemicircles harks back directly to the designs for glass light vaults, where the hexagons were needed for strength around the glass.
Originally this was a coal hole, but it's function now is uncertain.
East 73rd St. between Madison and Fifth in Manhattan. There is an identical cover in Chelsea - although I have misplaced the exact location -