BNE MSS/10146 (M) is a factitious manuscript composed of two parts, one from the mid-fourteenth century, which transmits the longest preserved fragment of the Historia troyana polimétrica, completed with passages from the Crónica troyana promoted by Alfonso XI, and another part dating from the end of the fifteenth century which completes the main narrative with a copy of the Historia troyana endorsed by Pedro I. The three texts convey similar medieval versions of the Trojan legend, since they share a common source, the Roman de Troie by Benoît de Sainte-Maure. In this paper, we will carry out a detailed study of manuscript 10146, including a codicological description, an analysis of its structure and of the articulation between its two parts. Furthermore, we will outline a possible history of its composition and circulation. In this way, we will prove the unity of the manuscript as a compilation of Trojan texts intended to provide a complete account of the story and preserve the fragmentary Historia troyana polimétrica.