An Early Pavement Filled Cover
The idea is simple, include a few necessary raised areas in the iron casting and fill the void with pavement to match the surroundings. It is unclear what the patent date refers too, as neither Maher or Flockhart are mentioned in the 1898 patent lists.
The design is simple and was widely used in the early 20th century, although today many exampes have gaps in the pavement fill.
The 6 hole design was widely used for sewers
This example is found on Amsterdam Ave about 137th St. in the repaved brick sidewalk in front of the julk of the CCNY North Academic Complex