The National Gallery, London, has just acquired an early 16th century altarpiece full of mystery, from its authorship to its iconography to its absolutely amazing razor-toothed, terrier-eared dragon, for 16.4m ($22m). This is a huge sum for an unattributed Old Master, but the price tag attests to the extraordinary quality of The Virgin and Child with Saints Louis and Margaret.The oil-on-panel altarpiece depicts the Virgin and Child enthroned under a richly embroidered cloth canopy. Behind her stand ornately painted pilasters topped with marble capitals carved with scenes from the Old Testament and others that have yet to be identified. The Virgin is flanked by an angel on each side, one playing a mouth harp, the other holding a hymnal. In front of the angels and to the sides are two saints: Saint Louis (King Louis IX of France) and Saint Margaret emerging from the broken body of the enraged dragon who ate her but couldnt stomach the cross she wore.The Virgin enthroned with angels and saints was a popular subject, but this rendition has a number of eccentricities that make it unique. Marys throne sits on plain wood steps, stark timber compared to the lush textiles and ornate decoration on the throne and pilasters. There are no other examples of plain timber steps in paintings on this subject from this period. Saint Louis metal sceptre, topped with a writhing mass of humanity, is far from the usual crown jewel. But most freaky of all is Margarets marvelous slobbering dragon. There are many dragons in Margaret iconography, some she emerges from, some she beats with a hammer, but none like him.Researchers think it was either painted by a Netherlandish artist or a French one. There are significant parallels between this piece and the early work of Jan Gossaert; i.e., the foreshortened faces of the angels and saints, the way the brocade and metalwork are rendered, the underdrawing techniques. The Netherlands hypothesis is also supported by the panel itself, which is Baltic oak. French artists used local wood. On the other hand, the presence of Louis, the specificity of his facial features, the meticulous detail in the Order of Saint Michael chain he wears, suggest a French artist. One possibility is the Master of Moulins, Jean Hey, known for his mastery of dramatic light and shadow and monumental figures who fill the space to the edges.The depiction of the chain is so precise it helps date the altarpiece. Dendrochronological analysis of the oak found that it the panel had to have been painted after 1483. The double knots (aiguillettes) on the Order of Saint Michael chain stopped being used in 1516 when King Francis I changed its design. This suggests the chain was painted from life before then. From other stylistic elements, researchers estimate a date of around 1510.The earliest documentation of the painted is a 1602 record of it in the Premonstratensian Abbey of Drongen (Tronchiennes) in Ghent, present-day Belgium. It was close to a hundred years old by then, but there is a possibility that it was commissioned for the priory church and had been there since the beginning. The Premonstratensian order revered Saint Louis for having granted them the right to bear the fleur-de-lis in their crest, and they are known to have dedicated an altar to the Virgin Mary and Saint Margaret in the Ghent priory in 1608. The painting itself may contain a hint. There are a pair of swans with entwined necks in the decoration on the right pilaster, and the swan was the monasterys central heraldic emblem.While it has been published before, the extraordinary detail and vivid palette of the altarpiece has never been reproduced in color until now, nor has the public had the opportunity to see its splendor in decades. It was privately owned and the last time it was exhibited was in 1960. The National Gallery was well-aware of its greatness, however, and has long yearned for it. Thanks to funding from the American Friends of the National Gallery, the museum was able to make its wish come true and acquire it in a private sale brokered by Sothebys.The painting goes on display on May 10th in C C Land: The Wonder of Art, the National Gallerys major rehang of its collection of Western European art, in the newly-reopened Sainsbury Wing where the museums earliest works are housed. You can devour the delicious detail of this altarpiece by zooming in on the high resolution image of it in the National Gallerys online collection.