I found this older French site
The crossbow seems to be quite small and possibly belonged to a well-known group of 16th c., mostly North Italian, crossbows which characteristically have steel tillers and were presumably used by assassinators, carried hidden beneath a cloak.
Of course it could also be a trap crossbow installed in the open.
They threw steel bolts and, like our sample in discussion, were equiped with a bow-'string' consisting of three steel links.
The tiller of this crossbow however seems to be of wood, with lateral iron reinforcements; the rear end terminates in a scroll pointing downward, which is also often the cas with the said Italian crossbows.
It is accompanied by a goat's foot sapnner.
So-called 'assassin's' crossbows in the Musée de l'Armée Paris and the Doges' Palace Venice attached lelow, one of them signed in full by the maker and dated 1562.