Dating of the mass has been controversial, with some scholars proposing a mid-career date, for example during Josquin's Roman period (roughly 1489 to 1495), and other scholars, such as Gustave Reese, arguing for an earlier date, claiming that the contrapuntal complexity the mass shows is more typical of Josquin's early style, and that he simplified his method as he aged. The earliest source containing the mass is the Vatican manuscript CS 197 (c. 1492–1495) In his 1547 Dodekachordon, Heinrich Glarean wrote that Josquin "composed the two L'homme armé masses to show off his skill."