The letter purports to be a response to a letter the king received from the clergy of Tours asking him if he would like to purchase an "imperial crown ("corona imperialis") made of gold and precious stones, fitting to his dignity" kept at their church. This letter ("literas") may not have been the first of its kind from Tours, for Alfonso refers in his response to their mentioning the crown "again" ("rursum"). It was delivered to the king by Sisnando, the bishop of Iria Flavia, who had received it from Mansio and Datus, two envoys of Tours, who had encouraged the bishop to persuade the king to buy. In this passage Sisnando is anachronistically titled archbishop, centuries before the see of Iria Flavia was raised to that dignity in 1120, under Diego Gelmírez. If the letter was copied after 1120, the error may be a "correction", intentional or not, to reflect the later status of Iria Flavia. It has also been suggested that the title "archiepiscopus" is an expansion of "æpiscopus" (bishop), a spelling known from contemporary Spanish documents, but of which a scribe working at Tours may have been ignorant and assumed the diphthong "æ" represented an abbreviation of "archie-". This variant spelling of "episcopus" is encountered in an original Asturian royal charter of 7 March 918. Alfonso accepted the offer and promised to arrange a "journey by sea" ("navalis remigatio") for May 906 (that same year) to make the exchange. The year of 906 is given in the "anno Domini" (AD) system of dating, rather than that of the Spanish era, then more prevalent in Spain. This is probable to be explained by the unfamiliarity of the recipients of the letter with his latter system of dating. While the "anno Domini" system was known in Asturias—and was used in a document recording the consecration of a new cathedral at Iria Flavia in 899—the Spanish era was hardly known outside of Spain, and even the Venerable Bede, "greatest computist of the early middle ages", was ignorant of it. It was planned to send members of the royal household to Bordeaux, where Alfonso apparently had connexions with the local magnate, Amalvinus, called "our friend" in the letter and titled both duke and count of Bordeaux.