In studies of recent decades about the origins of the Trecento chapel annexed to the church of San Galgano at Montesiepi, and about the commission of its mural paintings by Ambrogio Lorenzetti, two theses have clashed. The opposing arguments come to different conclusions about the date and the meaning of the frescoes. The reconstruction of the imagery in the triptych by Niccolò di Segna, once on the chapel's altar, and hagiographic research on San Galgano, demonstrate that the small altarpiece was destined from its conception for the chapel of San Galgano on Monte Siepi. The inscription, once on the frame of the triptych's central panel, becomes a primary source in this case. It declared that the patron of the painting, and of the entire chapel − both completed in 1336 − was Ristoro da Selvatella, an oblate devoted to San Galgano and associated with the familia of monks at the Cistercian abbey in the Val di Merse. Moreover, stylistic aspects of the frescoes are coherent with those of works realized by the great painter during the 1330s; one must keep in mind that Ambrogio Lorenzetti is documented at the abbey of San Galgano precisely in August 1334.