Like two other manuscripts that contain the ‘Legiloque’ version of the Dyalogue du pere et du filz, Vatican BAV Reg.lat. 1668 was once in the library of a Celestine monastery (a branch of the Benedictines). A 16th-c. note on f. 82v reads, ‘Aux Celestins de Marcoussis’ (‘To the Celestines of Marcoussis’). The Celestine house at Marcoussis, 17 miles south of Paris, was dedicated in 1408, some years after this manuscript was made. So where was it before?
Another inscription on f. 82v, this one from the 15th c., provides some tantalizing clues. A note at the base of the folio has been erased, but with the help of a UV lamp I transcribe it as follows: ‘Hunc librum tradidit in custodia quidam homo armoricus (?) natione britannicus vocatus Oliverius […]’ (‘A certain Armorican (?) man, of Breton nationality, by the name of Oliverius […] delivered this book into [our] custody’).
Unfortunately, the word following ‘Oliverius’ is covered by the stamp of the Vatican Library and remains illegible even under UV. The most I can say is that it doesn’t look as though any of the letters have lengthy ascenders or descenders.
Oliver the Breton’s identity remains a mystery, then. But the presence of his name does at least tell us something. Before reaching the Celestines, Vatican BAV Reg.lat. 1668 was almost certainly in the hands of an individual rather than an institution.