Through September 13, a brainteaser of an exhibition at the Metropolitan Museum of Art is testing visitors' talents for evaluating American decorative arts. The playful display was organized by American decorative arts curator Morrison H. Heckscher.

Nearly 35 armchairs, side chairs, tea tables, chests, bookcases, tall case clocks, lighthouse clocks, fragments, and supporting materials are included in "American Furniture and The Art of Connoisseurship." Objects on view range in date from the late Seventeenth Century to the early Nineteenth Century; in origin, from New England to Pennsylvania; in material, from oak to mahogany; and in execution, from carved to painted wood.

The examples - good, bad, and indifferent - illustrate four elements of connoisseurship: attribution, authenticity, condition, and quality. Understanding how these variables combine to affect value requires sophistication.

What is it? Where was it made? Who made it? Is it really what it purports to be? How has it changed since it was originally made? How good an example of its kind is it? These are the questions that dealers and collectors routinely ask themselves.

Sometimes, collectors must weigh authenticity against quality. Three Eighteenth Century Philadelphia tea tables illustrate that, however original, not every piece of furniture made in Colonial America was beautiful or well made. Most likely created by the same hand, the tables show the artisan's progression from promising beginner to skilled expert.

The subtleties of finish are pointed up by a set of Chippendale chairs made for Samuel Verplanck of New York. Divided among Verplanck's heirs, the chairs have been reunited to provide a lesson on the effects of refinishing.

Reproductions are another area of concern. Duncan Phyfe, the best known of New York Federal cabinetmakers, exerted considerable influence long after his death. Craftsmen such as Ernest F. Hagen copied both Phyfe's style and his construction techniques. A circa 1890-1900 armchair bearing the partial label of Ernest F. Hagen differs in at least one crucial respect: Hagen spliced the rear legs, something Phyfe almost never did.

Carving is an element to be judged independently of form and surface condition. Before the American Revolution, London-trained carvers came to Philadelphia to supply the local elite with the latest London fashions, that, for political reasons, could not be imported. The embellishment on two drawers taken from a Philadelphia high chest and matching dressing table prove how widely the quality of carving can vary.

"Improvements" ultimately diminish the value of an antique, as two Newport, R.I., tall case clocks demonstrate. One, dating to 1750, is by James Wady. Though refinished, the clock is structurally intact and unaltered. The other, by Wady's father-in-law, William Claggett, was "enhanced" with fluted quarter columns and cut-down to fit a room with a low ceiling. These revisions resulted in the loss of its once beautiful surface.

Most of the pieces are drawn from the museum's American furniture collection, begun in 1910. Inadvertently, "American Furniture and The Art of Connoisseurship" chronicles changing tastes and attitudes toward restoration, as well. As Heckscher notes, the "leave it alone" school has begun to overtake the "refinish it" school.

Not everyone will agree with the Met's conclusions, but that, says Heckscher, is the point. Instead of dictating his choices, the curator encourages visitors to decide for themselves.

Ultimately, not every question can be resolved through simple inspection. Connoisseurship today is as much a science as it is an art, relying on sophisticated diagnostic tools beyond the scope of this display.

On view in the Henry R. Luce Center for the Study of American Art, "American Furniture and The Art of Connoisseurship" was designed by Michael Langley. Graphic design is by Sue Koch; lighting, by Zack Zanoli. The show is open to the public on Fridays and Saturdays, 9:30 am to 9 pm; Sundays, and Tuesdays through Thursdays, from 9:30 am to 5:30 pm. The gallery is closed Mondays.

The Metropolitan Museum of Art is at 1000 Fifth Avenue, telephone 212/570-3951.