Shoe-gazing his way up 11th Street into North Philly on Thursday morning, Rick Spector paused at Pearl Street to marvel at something down on the corner.

Nearby were a rusty pole, spray-painted yellow arrows, and a carpeting of gravel, broken glass, mashed-in bubble gum, dried bird droppings, and flattened beer caps.

People look up for a reason.

But not Spector, who at 65 is a self-styled "Nortonist" — a person who classifies and catalogs manhole covers.

He and a friend coined the term in honor of Ed Norton, the sewer worker whom Art Carney played on The Honeymooners.

"Ooh, that's a really nice one," Spector said by the corner. "It's another high-pressure fire system from Clark's Foundry in 1925."

Commuting from Bucks County to the city for decades, Spector would get off the train at Jefferson Station and walk to his job at the Philadelphia Corp. for the Aging. He grew tired of the streetscape until his eyes began to register those dark iron discs with signature markings.

"I just started looking down at these guardians of the city's underbelly," he said.

Manhole covers are so ubiquitous that our brains can't be bothered to notice them unless one's missing or blowing off, due to underground pressure. They are everywhere, though, often a half-dozen a block, Spector said.

Some are worn smooth from traffic, paved over with asphalt, and rusted out.

"This one's just been obliterated," Spector said on Ridge Avenue.

Some covers, Spector said, can still tell a story, like 100-pound decoder rings that unlock the long-gone city of industry.

He's particularly interested in covers that were forged here in the J. Alfred Clark and Simon Scullin foundries.

Spector, who is retired,  recently made a five-minute YouTube video about the two foundries he called "Philly's Manhole Cover Kings," and a quick walk on a Thursday morning proved a point he tries to make in the video.

"Look down, you'll see thousands of their iron discs all over the city," Spector says in a voice-over.  "Scullin and Clark are unknown today, but their names may be written more in the book of Philadelphia than those of Ben Franklin and John Wanamaker."

Spector's not the only person out there Nortoning.  Thieves were targeting covers by the thousands during a scrap metal boom in 2008.

Artists have discovered their value as well.  Last year, the Inquirer profiled Russell Muits, a South Jersey graphic designer who used ink and canvas to make mandala-like impressions from city manhole covers.

"I didn't expect to love it so much," Muits said at the time.

Muits' travels show that many cities add a little flair to their discs — fishing and clipper ships by coastal towns, Native American art in Seattle.

In South Philly, some manhole covers on East Passyunk Avenue feature an "Indian Chief" in a headdress, but most owned by the city's water and gas utilities or Verizon and Peco feature a plain diamond-plated or basket-weave pattern.

A Peco spokesman said the agency owns 36,000 covers in a seven-county coverage area.

Spector said newer manhole covers rarely include the name of the foundry, and, even worse, some aren't dark or made of iron.

"It's sacrilegious," he said, looking down at a modern cover, a light-colored one that blends in with the sidewalk. "I guess that's progress."