After a decades-long quest, the Philadelphia Museum of Art has acquired a rare complete set of European horse armor - accompanied by an equally monumental suit of man armor - one of the last such sets remaining in private hands and the only one to be offered for sale in nearly half a century.

The 90-pound, steel-plated horse armor, crafted in 1507 for Ulrich of Wurttemburg, a flamboyant duke famous for his martial and marital affairs, as well as his allegiance to Martin Luther, will be unveiled in the museum's newly reconfigured Kretzschmar von Kienbusch Galleries of Arms and Armor on Wednesday afternoon.

The galleries, partially closed for reinstallation, will fully reopen the next day.

Acquisition of horse armor has been a museum goal since the days of Fiske Kimball, who presided over the museum when it first opened in its current location at the end of the Benjamin Franklin Parkway in 1928, officials said.

"The museum has always wanted to have an extraordinary horse armor to augment our holdings of European arms and armor, but finding one has been an especially elusive quest, given the exceptional rarity of this type of object," said museum director and chief executive Timothy Rub.

Rub said this particular set has been "well worth the wait." He credited the acquisition to the tenacity and discernment of Pierre Terjanian, associate curator for arms and armor.

Museum officials declined to provide the cost of the acquisition, which was wholly funded by Athena and Nicholas Karabots of Fort Washington and the Karabots Foundation.

Nicholas Karabots, a printing and publishing magnate, said he and his wife hoped the armor would strengthen ties between the museum and young audiences.

"We are especially excited about the impact . . . upon children as they come face to face with these astonishing armors, and look forward to the programs the museum develops as it shares the armors with families and school groups in the days ahead," Karabots said in a statement today.

Terjanian called it "the most important armor acquisition by any U.S. museum in the last 50 years."

It is, he said, unique work that had only been seen publicly during a brief showing in the 1970s in Switzerland. "Most living scholars have not had a chance to see it," Terjanian added.

The armor sets had been held privately in Europe since the eve of World War II. But as recently as the early 1930s, the horse armor was owned by newspaper magnate William Randolph Hearst, who acquired it in 1933 for 180,000 Swiss francs, a large amount for the time.

In 1939, however, Hearst was forced to sell to raise funds for his cash-starved newspaper empire.

Many items liquidated from the Hearst armor collection were acquired by famed collector Carl Otto Kretzschmar von Kienbusch, who subsequently bequeathed his collection to the art museum in 1976.

Ironically, the Hearst horse armor eluded Kretzschmar von Kienbusch, but has now rejoined many other pieces once owned by Hearst that are now part of the Kretzchmar von Kienbusch galleries.

The horse armor was created in 1507 by Wilhlem von Worms the Elder, a renowned armorer of Nuremburg. The man armor is the work of Matthes Deutsch of Landshut, who crafted it around 1505. About a dozen such field armors survive from that very early period, museum officials said.

The armor's original owner, Ulrich of Wurttemberg (1487-1550), was betrothed in 1498 to Sabina of Bavaria, the six-year-old niece of Maximillian I of Austria, the Holy Roman Emperor.

Ulrich married her in 1511, but his roving eye led him to strike up a liasion with the wife of a courtier. Ulrich killed the courtier in 1515.

The unhappy Sabina sought refuge with her brother, Duke Wilhelm IV of Bavaria, and Wilhelm subsequently led an invasion of Ulrich's lands, forcing Ulrich to flee.

In exile, Ulrich fell under the sway of Martin Luther and when he retook his territories, imposed the Reformation throughout.

Terjanian, the museum's armor curator, praised the quality of both horse and man armor and noted that its "exquisite decoration" demonstrates the "shift from the late Gothic to the early Renaissance styles" in Germanic territories.

"This is the only surviving early 16th-century complete horse armor to have been made in Nuremburg, and the only known example made by Wilhelm von Worms," Terjanian said. He characterized the quality of the decoration as "without equivalent among all other surviving horse or man armors of the time."