NEW YORK, SEPT. 9 -- A metal alloy that has been closely guarded as a family secret and passed from generation to generation has helped one company stay in business -- and in family hands -- for 364 years.

That makes Zildjian Co. of Norwell, Mass., the oldest U.S.-based company, according to a survey by Dun & Bradstreet Corp., which culled its business records to find existing firms that were operating before the United States was founded.

Zildjian has been making cymbals, gongs and bells for musical groups ranging from rock bands to the Boston Symphony Orchestra since it was established in the early 17th century. Its exclusive alloy of copper and tin gives the instruments "an unusual strength and brightness," says product manager Colin Schofield.

The company accounts for a resounding 70 percent of the worldwide market for musical cymbals, Schofield said.

While it was founded by Avedis Zildjian near what is now Istanbul, Turkey, in 1623, it was moved by his descendants to Massachusetts and incorporated there much later, in 1929 -- at the time of the Jazz Age.

But other long-time U.S. companies have their original roots in early America.

Dexter Corp., for instance, started out as a sawmill in 1767 in Windsor Locks, Conn., and grew into a Fortune 500 company traded on the New York Stock Exchange with revenues of about $650 million a year.

According to Dun & Bradstreet's research, Dexter is one of about 1,300 incorporated U.S. entities that were thriving in 1787, the year the Constitution was put together by the Founding Fathers in Philadelphia.