 The forger may have borrowed these exalted titles from the chancery of Alfonso VI, who was using the title "imperator totius Hispaniae" at the time.The subscription lists of both these charters (that is, the list of those who witnessed or confirmed them) are compatible with the dates, and it has been suggested that the clauses referring to Alfonso as emperor are derived from authentic (albeit now lost) charters.There exists a letter purportedly written by Alfonso III to the clergy of the Cathedral of Tours in 906, wherein the king is arranging to purchase an "imperial crown made of gold and precious stones, fitting to his dignity" ("corona imperialis") kept at Tours.