The market for Americana — which ranges from antique furniture to baskets to scrimshaw — has its share of multimillion-dollar objects that will grab headlines. But the real joys of the category lie in the stories behind the lots that will be sold this week at Sotheby’s and Christie’s.

The stars of the week are two intricately carved 18th-century tea tables. At Sotheby’s is a table created by the so-called Garvan carver, which was thought to be lost and now is estimated to sell for between $2 million and $6 million. At Christie’s is a Chippendale scalloped-top tea table once owned by the Stevenson family of Philadelphia. Estimated at between $1.5 million and $2.5 million, the mahogany table is generating excitement because of a recent surprise in the market. In October, Christie’s sold a similar table for the spectacular price of $6.8 million.

What could make a tea table worth so much money? In the Colonial era, furniture was a top form of conspicuous consumption. The carver’s art attracted attention, determined value, and conferred status. In Philadelphia, carvers were at the avant-garde of furniture design, creating a Rococo style and a distinctive “pie-crust” tea table with three legs and a flip top.

The Stevenson table is a fine example of the work from that era. But the $6.8 million table, which had been owned by the Fisher-Fox family of Philadelphia, had an edge: It was carved by a Philadelphia woodworker who had been identified by researchers and scholars as the greatest talent of his place and time.

His name is lost to history, but because his work was first noticed on a chest in the Garvan collection at Yale University, this anonymous master became known as “the Garvan carver.” Only 30 examples of his work are known to exist. The distinctiveness of his style to the expert eye is what makes his pieces worth exponentially more than superficially similar tea tables made by his contemporaries.

When Christie’s put the Fisher-Fox table up for auction, the house was so excited to have found a previously unknown Garvan carver table that it chose to illustrate its catalog with a long-lost example of the Garvan carver’s work. It is the same table that William MacPherson Hornor Jr.’s 1935 “Blue Book: Philadelphia Furniture,” a groundbreaking reference book, dubs “the acme of perfection.” It is also the table by which all other Garvan pie-crust tea tables are judged. But the antiques trade had lost track of the “acme of perfection” table. This is not uncommon in the world of fine furniture, where old families tend to hold on to their heirlooms and lose the thread of the market value.

In a strange twist, the inheritors of the “acme of perfection” table were getting ready to sell just when the Fisher-Fox table was being hammered down. They contacted an American furniture dealer to find out what their table was worth.

As with the Fisher-Fox clan, whose table had remained in the family since it was purchased in the 18th century, the existence of the “acme of perfection” table sent a wave of excitement through the American furniture world. In four months, two extraordinary examples of the Garvan carver’s work — one previously unknown and the other known but hidden — will have appeared on the market.

If the Sotheby’s table finds a buyer, being used for tea parties is probably not in its future, but neither is it likely to be put on a pedestal behind glass. For anyone in the relatively small universe of potential collectors, the table would be a showpiece for the home, placed somewhere highly visible in the living room or drawing room.

The lost-and-found drama of the tea tables, however, is not the only great story at Americana week. Sotheby’s silver department has its own detective story. In 1878, the San Francisco railroad titan Mark Hopkins died suddenly. His wife, who was then dubbed “America’s wealthiest widow,” had been in the process of decorating their dramatic mansion on Nob Hill. “Decorating was her preoccupation,” Sotheby’s silver expert, John Ward, said.

She became close to architect Edward Searles, a “cultured young man who shared her interests in art and design. This is one of things that brought them together. You might say that she collected him,” Mr. Ward said.

Searles, who was assigned to her project, resisted his client’s romantic advances for four years. Eventually, her persistence — and wealth — won out. They were married when he was 47 and she was 69. And though she only lived another four years, they built several houses together on the East Coast. Searles commissioned Tiffany’s to design numerous serving dishes, decanters, and flatware. Sotheby’s is selling a two-part centerpiece that was recently reunited by a collector and confirmed to be part of the Searles service. Separately, these two pieces — an intricately patterned receptacle for fruit or flowers and a mirrored plateau below that shows off the design work underneath the centerpiece — have sold for as much as $90,000 and $50,000, respectively. Now that they are together, and the Tiffany archive has confirmed the provenance with documentation, the lot is estimated at between $250,000 and $350,000.

But to have great value, Americana doesn’t have to be made from precious metal or come with a society pedigree. Christie’s will be auctioning hand-carved duck decoys this week with several estimated in the $500,000 range. What makes carved birds so pricey? “It’s the confluence of two collecting categories — hunters and folk-art collectors coming together and competing over the same material,” the head of Christie’s Americana department, Margot Rosenberg, said. Twenty years ago, a similar phenomenon took place with weather vanes. “Weather vanes was the old story,” Ms. Rosenberg said. “This is the new story. At auction, a bird has yet to break a million, but one will soon.”