France and Mexico celebrated their friendiversary by exchanging ancient books.

At a recent meeting, French president Emmanuel Macron and Mexican President Claudia Sheinbaum conducted a highly symbolic book swap.

To commemorate years of diplomatic relation—and sure, with an eye to continued trade—France and Mexico exchanged two ancient manuscripts: the Codex Azcatitlán, and the Codex Boturini. 

Both texts depict the Aztecs’ migration to Tenochtitlan (or, present day Mexico City). But the Azcatitlán has been kept in Paris’s Bibliothèque Nationale de France since 1898.

That manuscript dates from around 1519, just after the Spanish touched down in Mexico. Composed of pictograms, the Azcatitlán’s 25 folios feature a succession of Aztec rulers, and dramatize the arrival of Hernán Cortés and Christianity.

According to the Library of Congress, “of all the known manuscripts recounting Aztec history, the Codex Azcatitlán is probably the most valuable and important.” So it’s pretty nice of France to give it back.

The Boturini has roughly the same origin story as its brother, though historical consensus suggests it was drafted a little later—between 1530-1541. Housed at Museo Nacional de Antropología in Mexico City since 1871, this codex follows the Aztec migration from Aztlán to the Valley of Mexico.

Also called “The Pilgrimage Strip,” its origins are a little murkier than the Azcatitlán’s. Mesoamerican scholars believe this anonymously authored manuscript was unfinished, for mysterious reasons.

As ArtNews’s Leigh Anne Miller reported Tuesday, the swap is historically auspicious because the codices are rarely on public view, and rarely travel. It’s particularly meaningful on Mexico’s end, given the country’s long quest to repatriate Mesoamerican cultural objects that have “found” their way into collections across the pond.

Ball’s in your court, Europe. As Emilia Mendoza, a Mexican restitution activist, told The Art Newspaper: “The loan is a good signal, but we want something permanent.”