New York’s ever-changing streetscape usually changes at a pace too slow to be discerned. All appears as it was the day before, until the day comes when you realize how long it has been since you’ve seen ...

A privilege sign.

And you have seen them, though you probably don’t recognize them by that name. You may not even know that there is an industry term for the promotional signs installed by large corporations — usually soft-drink companies, most often Coca-Cola — on mom-and-pop storefronts.

Privilege signs once could be spotted everywhere. Now, they are few enough to be tracked like endangered species. And people do.

“I get a lot of traffic for those old signs when I put them up on the site,” said Esther Crain, the creator, producer, editor, writer and photographer of Ephemeral New York, a Web site that has tracked remaining privilege signs.