A Bigger Issue Revealed by the Cortés Letter Unbeknownst to many, this letter had long been in possession of the AGN. But it suddenly showed up on the ‘for sale’ list at Swann Galleries, a prestigious antique auction house located in New York City. A letter from Cortés to his assistant which was sold for $32,500 in a 2019 auction. ( ) The researchers had been searching auction house websites in multiple countries, on the lookout for Cortés documents specifically. Between 2017 and 2020, several auction houses began offering documents for sale that related in some way to the famed sixteenth century conqueror of Mexico. This was suspicious, since similar documents had been scarce in years past.