Which came first the B or the D
This is probably a sewer lid dating to the time of consolidation, around the time that Richmond County was taking on the guise of the Borough of Richmond.
The design is the by then standard honeycomb sewer lid with a particularly lively SEWER inscription. The lower lettering seems to be a D that has been converted into a B, maybe the old Sewer Department became the more debonair Bureau.
No hiding what's below this honeycomb.
There are many honeycomb covers in New York and on Staten Island, although I have not found an "uncorrected" B or D cover. This one is on Giles Place and Sheridan Avenue in Grasmere, Staten Island.