26 June 1944, during the allied bombardments of France, the town hall and Bibliotheque Municipale of Chartres were severely damaged. Fifty six people died that afternoon, thirty were injured, and out of the approximately 500 medieval manuscripts kept in the library only around 177 survived, many of them heavily carbonised.
Images from Collection Claude Warconsin
Among the destroyed manuscripts was a collection of fragments of Greek manuscripts originating from the Great Laura on Mount Athos. These were brought to France by the art historian Paul Durand (1806-1882), who traveled to Thessaly and Mount Athos in 1839-1840. The circumstances are unclear, but the famous manuscript dealer and forger Konstantinos Simonides (1820-1890) may have been involved. The fragments entered the Chartres library after Durand's death. One of the fragments, consisting of six folios, was furnished with Byzantine musical notation of an archaic type, which later became eponymous of one of the two main varieties of the Palaeobyzantine musical notations, the so-called 'Chartres notation'.
Fortunately, images of the Chartres fragment were taken and copies are preserved in the Archive of the MMB.
See further description and images of the Chartres fragment here: Link