Described by the index compiler (probably a monk working in the Palaeography Workshop in the Benedictine Abbey of Solesmes) as ‘Bréviaire noté d’hiver Metz 461‘
This manuscript (dated mid C13) was lost in a bombing raid on the city of Metz (a city in northeast France) in WWII, but survived in a microfilm made by the Abbey of Solesmes in the interbellum years (possibly earlier) to support their research into Gregorian chant restoration. At time of writing (end 2019) we are far in the process of making a transcription of the manuscript’s notation into the square-note neume notation now used in Gregorian chant. Watch this space for more information on this effort.
Index notation: Officium proprium de Scô Gengulpho 438 verso (editor: office ends at 444 verso)