Brooklyn Mystery Cover
There are two of these mystery covers on two sides of Brooklyn Borough Hall. Of course Borough Hall was City Hall before that fateful day in 1898, so that could be the CH. The BP then would not be Borough President but it could well be Bureau of Parks, with a slightly grandiose "of."
The fairly open grid pattern is widely seen around the city. The circular badge is often used for electrical lines in municipal locations.
This lid is located on Fulton St. in back of Borough Hall.