This Missale Speciale Sedunense was written for the Sion bishop
William of Raron (Guillermus de Rarognia) († 1451) in 1439 by
Johannes Thieboudi. The parchment codex contains, in addition to a
calendar, the Proprium de tempore, the Ordo et canon missae, the
Commune sanctorum, the Proprium de sanctis (from Hilarius to Thomas
the Apostle) and the Missae pro defunctis. An appendix includes
three votive masses.