None of the works in the show are weighty with metal. A pair of pre-Columbian gold earrings - elongated diamonds hooked into half moons -are feather-light works devised about A.D. 800 by an artisan in an area in modern-day Colombia once known as Sinu. Other earrings, a number of rings and a Peruvian necklace are made of hollow gold elements. A Chimu necklace, made after A.D. 1000, uses hollow gold balls - a shade smaller and dented in much the same way as worn Ping-Pong balls are.

One starkly simple ring comprises an undecorated band of gold that widens to frame an oval crystal with a frosty glow probably heightened by an unseen foil backing. In ancient jewelry, the underside of stones are always covered - a practice that changed by the Renaissance, Mr. Merrin said. Some other noticeable differences between the rings shown and those made today include the modest size of the emeralds, garnets or pearls employed and the unembellished settings. Most of the time, the metal merely seems pressed down on the edges of the stone to secure it in place. The effect is most attractive.

In this dealer's view, elaborate decoration on the surfaces of jewelry may hide imperfections of crafting or design. ''A ring that is perfectly simple is what it is, and there is no hiding its shape or the way it was made,'' Mr. Merrin said. ''You can't make a mistake on such works. If you put in a lot of curlicues, you can make a lot of mistakes.''

There are several exceptions to the rule of undecorated surfaces - but none have curlicues. The most arresting is a large pair of fifth century A.D. Persian gold earrings, hollow hoops enriched with twists of wire and granulation.

''I don't know how they drew hair-fine wire like that,'' Mr. Merrin said, marveling at the detailing on the earrings as well as on a seventh century B.C. neo-Assyrian stickpin, which is a cube of the gold-and-silver alloy electrum topped by a milky quartz ball of chalcedony. The cube, deftly wrapped with metal wire as delicate as a spider's web, is an inch-high stack of tiny boxes crafted of electrum enhanced by bow-tie images on all four sides.