The four music instruments created by Antonio Stradivarius more than 250 years ago are appraised together at $50 million. Now, thanks to a New Jersey book publisher, they will belong to the National Museum of American History.

Herbert R. Axelrod and his wife, Evelyn, also gave a $1 million endowment with the two violins, a viola and a cello. The money is to help the museum, a part of the Smithsonian Institution, maintain the instruments, together called a quartet, for exhibits and performances.Smithsonian players already have made recordings of performances on the instruments, including a string quintet by Franz Schubert. The museum has announced recitals for May 30-31 to include music by American composers George Gershwin and Charles Ives as well as Beethoven and Brahms.

The museum has had the Stradivariuses on loan for 12 years. They will become property of the museum over the next three years under a contract signed in December, James Weaver, head of the museum's cultural history division, said Thursday.

Gifts of this kind are often spaced out over years to maximize tax deductions for donors.

Axelrod, 70, founded TFH Publications Inc. of Neptune City, N.J. TFH stands for Tropical Fish Hobbyist, the name of the firm's leading magazine.