The oldest cover in New York?

This unusual hexagonal coal hole cover and vault light could be the oldest cover of any sort still working on the streets of New York (in this case in Brooklyn.) Cast by the prolific ironman John Black Cornell and his brother William Wesley Cornell, whose foundry started in 1847 at 143 Centre Street in Manhattan. The date on the cover, Feb 19th, 1856, refers not to the date of manufacture but to the date of the patent granted to J.B. for a method of attaching glass plates to an iron frame (it involves fire and brimstone!) The glass plates have long been replaced by concrete and wood plugs, but when new, the plates allowed sunlight to penetrate into the vaulted area below. The whole lid in turn could be lifted open to allow the delivery of coal. Both the use of coal for heating and the glass vault light were signs of a well-to-do household in the newly developing suburb of Brooklyn Heights.
The age of the cover itself is uncertain. The JB & WW Cornell foundry opened a new larger foundry on West 26th Street in 1859, and this would bracket the age of this cover from 1856 to 1859. However, the intrepid researcher Walter Grutchfield has found advertisements for the firm dating into the 1880's that continue to use the Centre St. address. Also, The building currently at the site was built in the 1900's and it is uncertain if the coal hole and cover was used by the previous structure. Is this an interesting look into 19th century Brooklyn? Sure. Is it a look back to the 1850's? Could be.