Many American antiques were never marked or stamped by their makers, so dealers and collectors have to judge authenticity by other means.
Antique pieces mature over time, acquiring characteristics that are evident to the experienced eye. In addition, pieces from the Colonial era tend to have distinct structural differences from pieces made today or even a century ago.
Renowned antiques dealer Albert Sack, of Israel Sack in New York City, shows Martha several early American antiques and their later counterparts, using the pairs to illustrate what to keep in mind when determining authenticity.
There are a few general rules of thumb to keep in mind when inspecting a wood piece: As wood ages and is exposed to air, it grows darker due to oxidation, and will develop a warm, deep patina with time; the sharpness of the edges and the carving on a piece soften subtly with exposure and handling; and wooden pieces lose moisture, eventually shrinking along the grain.
Albert draws Martha's attention to two beautiful wooden card tables, one from the 1790s and another from around 1920. The two appear nearly identical, but when he turns them upside down, he points out a key difference: The older table exhibits a patina where it is unfinished, while the 20th-century piece is stained underneath, in an obvious attempt to fake the appearance of naturally aged wood. The older piece also has more integral construction, using one piece of wood where the newer piece uses several.
Albert then uses a McIntire side table from 1810 to show the natural pattern of oxidation in drawers; the underside of the bottom drawer is darker in color than that of the top drawer, which was more sheltered from the air. Another telling detail indicating the table's age is that the bottom panels of the drawers have shrunk, causing the drawers to be somewhat loose in their casings.
Next, Albert inspects a Queen Anne wingchair from around 1740. On an antique chair, the upholstery or fabric covering is seldom original; the frame is what is important, and you cannot judge the frame without opening up the upholstery. Compare the exposed parts of the frame to the parts that have been covered with upholstery: The exposed parts should be richer and darker due to oxidation.
Some of the pieces we think of as "fake" were probably not originally created to fool the buyer, but rather to round out incomplete sets of the real thing, or as a tribute to a style. Unscrupulous dealers sometimes try to pass off later imitations as the real thing, however, so buy valuable antiques only from a reputable dealer, educate yourself about the structural characteristics of the style and period you're considering, and make sure you get a written guarantee of a piece's age from the seller.