Gem Spa had been open for only 40 minutes before the first tour group of the day came by. It was early on a Saturday, and a potbellied guy with bleached blonde hair and a goatee who calls himself Bobby Pinn was lecturing to a devastatingly bored preteen and four adults who did not seem to know what he was talking about.

He was explaining the concept of an egg cream — the quintessential New York fountain drink that some people say was invented at this location. “It’s very refreshing,” he said. “Almost like a Yoo-Hoo.” Then Mr. Pinn flipped through a laminated book to show the tourists a black-and-white photo of the New York Dolls posing in front of Gem Spa’s iconic signage before shifting gears.

“You guys watch Woody Allen movies?” he asked, leading the group further down the block. No one on the tour entered Gem Spa, and no one bought anything.

This is the current state of what is possibly New York’s most famous corner store, which first opened in the 1920s and was given its current name by its second owner sometime in the 1950s.