The lack of a systematic classification of the old manuscripts preserved in Spanish libraries has made it exceedingly difficult to come to definite conclusions about which tendencies were predominant in the elaboration of Lat-in codices throughout the centuries. Nevertheless, in the past few years several studies addressing this issue have been published. This paper hopes to contribute to that line of research by presenting a Codicological and Paleographical study of manuscript A 331/143 of the Library of the University of Seville containing a Ro-mance version of the Spanish Chronicle Historia de rebus Hispaniae, also known as Historia Gothica, written by the Archbishop of Toledo Rodrigo Jiménez de Rada (1170-1247), which, on the other hand, has been systematically overlooked by those who have concerned themselves with the study of the Textual Tradition of the said chronicle.