Opening day at contemporary art fairs signals a mad search for future art stars. Eager to scoop up the newest, freshest, and brightest prospects, collectors focus on the wettest canvases, whipped up by artists with newly-minted MFAs. Yesterday afternoon, at the world’s biggest art and antiques fair, it was the oldest folks who were the star attraction. As a light dusting of snow coated Maastricht, collectors and curators streamed into the massive convention center, bound for stands bearing Old Masters.

The crowd was definitely Euro. Men with gold pinkie rings and three-piece suits puffed on cigarettes and gazed at Miros and Rubenses through screens of smoke. Women with diamond earrings, silk scarves, and elegant fur-trimmed suits sipped champagne and shopped. French, Italian, and German could be heard up and down the aisles – each named for chic shopping locales around the world, from Place Vendome, Via Veneto, Domplatz, Fifth Avenue, New Bond Street. The rich from all over the world are certainly made to feel right at home in Maastricht.

Old Master dealers had brought their best, set up stands with elaborate velvet wall-coverings and brocade curtains, and survived the notoriously rigorous vetting process. For two days before the fair starts, a cadre of curators, dealers, and experts review the entire show. They check for authenticity, dating – everything a dealer represents about a work. While vetting is standard at many fairs, it can be a formality that is not taken seriously. At Maastricht, it is excruciatingly thorough, which gives buyers confidence they are buying good goods.

The Maastricht fair gives dealers a reason to save up prime material and debut it at the fair. New York dealer Jack Kilgore featured a history painting by two Dutch artists, Hendrick van Balen and Jan Brueghel the Elder, “Moses Striking the Rock” (c. 1608-18), priced at $1.25 million. It is an exercise in connoisseurship to sort out the details of this collaboration: van Balen’s Mannerist, elongated foreground figures, supported by Brueghel’s atmospheric blue sky and leafy green foliage background.

Mr. Kilgore called the collaboration “seamless,” and indeed it doesn’t look like an assembly-line piece so much as a team effort. The Getty is interested in borrowing the work for an upcoming show about such collaborations, according to Mr. Kilgore. This unusual work, created with oil on copper, is typical of the sort of atypical work Mr. Kilgore is known for selling. He gravitates to the tough pictures – graphic religious imagery, cerebral history painting, and portraiture.

In a period where the Old Master supply continues to dry up, selling the quirky might be a means to survival. “There used to be endless still lifes with tulips,” said the director of the van Gogh Museum, John Leighton. About a decade ago, the fair attracted the upper-middle-class buyer, says Mr. Leighton, “looking to buy something which fit in the boot of a BMW.” These days, the fair has turned into a serious international hunting ground for museums and major buyers.

Another New York dealer (though they are the minority) says he focuses on the offbeat because that’s what the buyers like. “It’s our taste and what we’ve stumbled into,” said Henry Zimet of French & Co. “We like things with an edge, we like the eccentric.” Mr. Zimet’s booth is nothing if not dramatic. Warm raspberry walls set off an astonishing mix. One wall is devoted to Dutch art. A giant floral still life (c. 1730) by Jan van Huysum, priced at $12 million, anchors the wall – perhaps one of the most expensive bouquets in Holland (which exports 80% of the world’s flowers). There are dewdrops on petals and flies, butterflies, and ladybugs – enough bug life to excite any exterminator.

London dealer Derek Johns reserved a special spot for an unfinished painting by British artist William Hogarth. “He lunged straight in,” said Theodore Johns, son of the gallery’s founder, of the free brushstrokes used to render the lascivious glance of a young man for a young maid in this scene from “The Rake’s Progress,” available for $220,000. Across from the Hogarth, Mr. Johns displayed a small gold ground crucifix, once owned by famed collector Adolphe Stoclet. The gallery recently sold another crucifix, also originally owned by Stoclet (who owned the Duccio now at the Metropolitan), which they bought last year at auction.

Auction material is usually tucked away before appearing back on the market. But New York dealer Adam Williams brought his newly acquired painting of the Duchesse de Montebello by Baron Gerard – bought in January at Sotheby’s. Another familiar work from auction appeared in the booth of Belgian dealer Axel Vervoordt.

In a room designed to simulate a chic dinner party, with a cascading crystal chandelier dangling over a table laid with china, fruits, and crystal, hung a painting familiar from Sotheby’s Bill Blass auction. Blass was known to shop at the Belgian dealer’s gallery, but in this case of a reverse commute, the painting went from Blass to Vervoordt. The 1666 painting by Jacob Biltius, a composition of guns, spears, and other ancient weaponry, is priced at $575,000.

While many of the Old Master dealers are old masters themselves, 28-year-old Fabrizio Moretti is one of the younger turks in the business, selling some of the oldest works at the fair. Moretti Fine Art, based in London and Florence, specializes in Italian Renaissance panels. Works from the 14th and 15th century dotted his stand, glowing under spotlights. A stunning crucifixion triptych by Jacopo di Cione hung beside a panel by Bernardino Zaganelli of a Madonna and angels.

The Zaganelli was once owned by a prince from the famous d’Este family. Both pieces are priced in the seven figures. Mr. Moretti says he chose to specialize in these Old Masters because they are the best of what Italy has to offer. Listening to Mr. Moretti speak about his paintings, they don’t seem old at all.