The DSI in Harlem
The Departmant of Street Improvements was formed in the Northern 23rd and 24th Wards, (what is now the western Bronx) in 1890. This cover may indicate that the department was sharing resources with the Manhattan-centric Dept. of Public Works, which was building sewers in Manhattan at that time.
This is the classic 8 circles around a center ring with a linking bar, with 9 vent holes - a Bronx ferris wheel.
Sewer cover in the expanding sewer system of the 1890's.
This design is found throughout the western Bronx. This example is on West 126th St west of Morningside Ave. in Harlem, Manhattan.