The PBS series "Antiques Roadshow" hit one out of the park after someone showed up with a collection of pristine 1870s Boston baseball memorabilia.The treasure trove of signatures and rare baseball cards from Boston Red Stockings players was appraised at $1 million for insurance purposes, series producer Marsha Bemko said.She said it's the largest sports memorabilia find in the history of the 19-year-old public TV show, which travels America looking for varied heirlooms and treasures.The valuable collection was brought to an "Antiques Roadshow" taping Saturday in New York City. The owner inherited it from her great-great-grandmother, who ran a Boston boarding house where the team lived in 1871-72, PBS said.The owner's identity was kept private for security reasons, PBS said Monday. The collection had not been formally valued before but the owner had once been offered $5,000 for the cache, according to PBS."Antiques Roadshow" appraiser Leila Dunbar, says the "crown jewel" of the items is a May 1871 letter to the Boston landlady that includes notes from three future Hall of Fame members: Albert Spalding, the future sporting good magnate, and brothers Harry and George Wright. The letter included the players' appreciation for their host's cooking.The baseball franchise is now the Atlanta Braves — the only one of today's 30 Major League franchises to have fielded a team every season professional baseball has been in existence.Appraisals from the New York City visit will be featured in three hours of "Antiques Roadshow" episodes to air in 2015 on public TV stations. The series is broadcast on Monday nights.