If i remember well, B.I. is more interested in a determined model from a determined period, preferrably with pictures.
If the question were how soon in time did Muslims
use crossbows, or how soon in time did Musliums
make crossbows ( which is a different thing for the matter ), various apparently solid sources could be considered.
You have the Southern Italy Saracens, whom were not fond of the crossbow use, although their artisans used to produce them for Christian Forces:
http://www.deremilitari.org/resource...en_archers.htm
but you also have strong traces of Muslims using Crossbow versions against Christians, namely in the Reconquest period. I will try and attach herev the scanning of part of a letter, written in Latin, by an eye witness of the Conquest of Lisbon in 1147, where the Moors were already equiped with crossbows.
I keep searching the track of the so called moorish "Cuçalarab", a light crossbow from the Reconquest period, so eficient that the Christians have copied it for their own use.
Kind regards