Antonio Stradivari (1644-1737) was a renowned master luthier (maker of stringed instruments) who made about 1,200 stringed instruments, each of them by hand. Today, more than 270 years later, only about half the instruments he made are still in existence. Virtually all of them are accounted for. Auction prices of $3.5 million per Stradivarius are not uncommon, but the actual sale of a Stradivarius is rare. Two Stradivarius violins are on display at the Smithsonian Museum of American History in Washington, D.C. Three are held by the U.S. Library of Congress. Music historians are nearly unanimous in the belief that Stradivari produced his finest work between 1698 and 1725. Although Stradivarius violins were made until his death, many made after 1730 are believed to have been crafted by the master's sons, Francesco and Omobono. An expert is almost always required to authenticate a genuine Stradivarius.
Know that fakes are rampant in the shadow world of musical instrument collecting. Finding a Stradivarius label in a violin is virtually meaningless, as a cottage industry in the manufacture and installation of bogus labels inside musical instruments has thrived for centuries.
Look for the traditional Stradivari label, which contains a Latin inscription, "Antonius Stradivarius Cremonensis Faciebat Anno" to denote the violin maker's name, the town (Cremona) where the instrument was crafted and the year followed by a month and day, either printed or handwritten. Even this label is no assurance the instrument is genuine.
Hire an appraiser who will be worth the money if you possess a genuine Stradivarius. Otherwise, be able to identify 270-year-old spruce and maple and varnish stains and textures. Stradivari also imbued his woods with minerals, including potassium silicate, Bianca, potassium borate and sodium, to enhance the sound properties. Sophisticated chemical tests that cannot harm the instrument are required to establish authenticity. Contact the American Federation of Violin and Bow Makers to locate an expert appraiser (see Resources).
Realize that hundreds of thousands of violins have been manufactured in the last 300 years using the methods and designs pioneered by Stradivari. You have a better chance at uncovering an excellent Stradivarius copy (which may also be worth some money) rather than an actual instrument built by Stradivari himself.
Review research by the Smithsonian Institution, which states that "a violin's authenticity can only be determined through comparative study of design, model, wood characteristics, and varnish texture." Authentication requires extensive testing and comparisons by an experienced violin maker.
Don't purchase any rare item without consulting a trusted, impartial expert.