The shop has not been keeping regular business hours. Instead, Ms. Eisenberg takes to Twitter (@precs) or Instagram (permanent_records) to tell vinyl hounds when she will be open — often from noon to 7 p.m. (Starting in November, she said, she will experiment with staying open Wednesday through Saturday.) She also rolls a sign up the hill out to Fifth Avenue; its plastic letters declare, “We buy records.”

“We’re here more than people think,” she said.

Lee Margolis, 47, hauled a cardboard box of records to the shop one recent Saturday, hoping to sell the collection that his friend had found abandoned on a stoop. Ms. Eisenberg thumbed through the sleeves, then opened them to inspect the condition of the records. Most were scratched or warped. Ms. Eisenberg offered him $25 for the lot. “There’s nothing I’m dying to have,” she told him. A new record enthusiast, Mr. Margolis took the deal, trading the records for jazz standards. “I have a total of eight albums,” he said. “But I have an 11-year-old and 6-year-old, and when I put on the Beatles or Fleetwood Mac, everything’s calmer.”

Some customers followed the shop from Greenpoint, while others come in looking for something specific. Chase Mazo, 16, was on the hunt for a Pharcyde album. (The West Coast hip-hop group was featured in his French textbook.) He came down from Park Slope with a friend, bike helmets in hand. “My birthday was a few days ago, and I have some money to spend,” he said. He had picked up the shop’s business card at Monk, a local thrift shop. The card was tattered, having spun through multiple wash cycles stuffed in the pocket of his jeans.

Others amble in after seeing the chalked-up sandwich board propped outside. Mario Delgado, 41, stopped on the way to pick his children up from school. “I used to have about 1,000 gospel records, but I had to get rid of them because we traveled so much,” said Mr. Delgado, a Marine on the brink of retirement. He recently relocated with his family from San Diego to Bay Ridge. “Now,” he said, “I’m rebuilding my collection.”