Roman crossbow

[D B Campbell]

In the book, Ancient and Medieval Siege Weapons by Konstantin Nossov, below drawing shows how string of bow is notched on the stock of crossbow.

Doesn't the drawing depict a gastraphetes?

The drawing has been lifted from Marsden's Greek and Roman Artillery (1969), with the addition of little hatched lines down either side of the stock to represent the ratchet. Marsden's drawing is labelled "Fitting the bowstring to the gastraphetes". Nossov acknowledges that it is Marsden's drawing in his English edition (p. 135).