SALISBURY, England — In this sedate cathedral town in the west of England, an old teapot with a missing lid and a repaired handle sold at auction Tuesday for 575,000 pounds with fees, or about $806,000. The winning bid was made in the room by Roderick Jellicoe, a London dealer, on behalf of the Metropolitan Museum of Art in New York, after a tense eight-minute duel with an American private collector bidding by telephone. The presale estimate had been £10,000 to £20,000.

Clearly, this was no ordinary teapot.

The auctioneers Woolley & Wallis had recently attributed the piece to John Bartlam, an enterprising potter who produced blue-and-white-decorated soft-paste porcelain at the Cain Hoy factory in South Carolina in the late 1760s. The Staffordshire-trained Bartlam left England for South Carolina, drawn by its plentiful supplies of local kaolin clay and its wealthy consumers, according to the salesroom catalog.

In the past 10 years or so, following archaeological excavations at the site of his factory, scholars have recognized that Bartlam’s porcelain was the first to be produced in America, predating the better-known Bonnin and Morris wares made in Philadelphia from 1770 to 1772. This Salisbury auction house was therefore offering what is thought to be the oldest known American porcelain teapot.

“It’s extraordinarily important for many, many reasons,” said Alice Cooney Frelinghuysen, the Anthony W. and Lulu C. Wang curator of American decorative arts in the American Wing of the Met. The teapot’s use of local clays “represents the entrepreneurial spirit of 18th-century America,” Ms. Frelinghuysen said.