The classic honeycomb design spread from Brooklyn over the Narrows to Staten Island in the early 20th century. This cover has the maker inscribed on the rim, the Staten Island Shipbuilding Co. a company that originally made wooden ships, but started a Foundry Division in 1916 and merged with another company to form United Shipyards in 1925, giving a fairly firm dating for this cover.
B of R is of course Borough of Richmond, Staten Island's official borough name until the 1970's, with the SEWER letters adding a festive note to this celebration of local industry.
Department of Sewers under the Borough President of Richmond.
The honeycomb pattern is found around the city, B of R only on Staten Island. This example, with the Staten Island Shipbuilding Co. S.I and Foundry Dept. inscription is near the appropriately nautical sounding intersection of Sands and Wave in Stapleton.