George Harrison visited the store, Mr. Jay said. Joni Mitchell bought an antique mandolin there and then wrote about the purchase in a song. Bob Dylan, Bruce Springsteen and Peter Buck, formerly of R.E.M., are among those said to have ordered instruments from the shop.

Although the family is resolved to sell Mandolin Brothers, there have been occasional pangs. Eric Jay said that he was recently obliged to turn down a consignment arrangement for what he termed “the holy grail of mandolins”: a 1922 Gibson F-5 signed by the storied luthier Lloyd Loar, worth $200,000 or more.

There have also been happier moments. While going through the inventory, Ms. Reilly said, she came across an unfamiliar brown 1957 Gibson Les Paul Jr. A short time later, a man called and said he had left such an instrument there for repair in 1991. After an unusual sticker on the body of the guitar featuring a rifle crossed with a long-stemmed pipe helped identify it, plans were made to reunite the instrument and its owner, Don Rogers.

“I was dumbfounded,” he said in a telephone interview, describing his reaction upon learning that the shop still had the guitar. “I almost fell on the floor.”