Nancy Wu, a museum educator who’s been at the Cloisters for two decades, finds the “AE” cipher most perplexing of all. Often appearing near a hanging’s center and at its four corners, the insignia also materializes on dog collars and in other discreet places in the works.

She told me there are three general theories about the mark, noting that initials in the Middle Ages were sometimes derived from the first and last letters of one name. Some believe it signifies Adam and Eve, while others have claimed it identifies Anne of Brittany, a major patron of the arts who was active around the late 15th century and who, in 1499, married King Louis XII of France—a fitting occasion for the tapestries to celebrate.

A more recent theory conjectures that the letters represent Antoinette of Ambroise, the wife of François de La Rochefoucauld’s second son, Antoine, who was born around 1475. Since the tapestries were undoubtedly at the de La Rochefoucauld castle in 1680, this theory is particularly tantalizing.

“One of the main questions people ask is how long it took to make them,” Wu says. “Each tapestry was probably stretched over one enormous loom. But there’s no way of answering without knowing how many people were on the loom, and how many looms were worked on at the same time.”

Tapestries are woven with colored thread called the weft, which is wrapped around long, strong threads called the warp. Medieval tapestry weavers, usually young men, worked side by side in teams, using small tools. They worked only by daylight, as candlelight might distort the thread colors. A skilled weaver might complete one square inch in an hour. Wu estimates that one tapestry could have taken months, if not a year or two, to complete.

The impeccable quality and technical achievement of the hangings suggest a prosperous patron commissioned a superior workshop for the project. “Tapestries were status symbols,” Wu says. “It was more expensive to purchase a tapestry than build a castle.”

She had the rare opportunity to see the flip-side of the hangings in the 1990s, when they were removed so that the gallery could be renovated. “The backs looked like the complete reverse of the front. You’d expect to see shaggy, cut-off threads, but these were unbelievably finished,” Wu remembers. The reverse also revealed some fading of the original colors: The now-dark forest, for example, was once a tender, early summer green.