There are O's on manhole covers that say "Consolidated Edison," which isn't the sewer company. I didn't find a pic of the ConEd cover, just a generic photo to illustrate what a manhole cover is.
Oops. Well, it's a good thing it didn't happen here in my town. The Anacortes sewer system manhole covers say "ASS" on them. Seriously.
Here's a whole page full of them.
http://www.forgotten-ny.com/STREET%20SCENES/manholes/manhole.html