Miniature Ballista

 I bought this from a "Fine English Sporting Guns and Rifles" auction. The attached label doesn't give much info, and the string is broken. I'm hoping to figure out how it works and get it going. It should provide many hours of fun. The trigger mechanism has virtually no wear on it, so I'm assuming it was made for the fun of it or as a demonstration of the workers skill. Probably Victorian?
The arms that the string attaches to look rather short to me and there is no obvious way to pre tension the skeins of sinew. The 'wings' can fold back or forth and this may provide a way of stringing and pre tensioning.

Here's a transcript of the info that came with it written on 2 tiny labels.

Text broken int 4 sections corresponding to the 4 sides sides of the two labels. My comments in italics

Ballista/
Steel with folding “wings” :-
Origin and age not known, but animal-like sight looks oriental as does decoration:-
Fitted with 14^th century European pattern revolving nut; but the groove in the stock is flat, not curved as in medieval bows to cut down friction; if the bolt was flighted it would have to be less than ¾” across to clear the columns in the central window (to be in scale the flights would be about 5/8”
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across, with 3 flights) ; Winding handle may be in Ivory but more likely in Ivorine an early plastic;
Ones first impression is that it is French, the steel ‘stem of the handle’? is half-heart shaped, elegant and ‘resolved’? ; Fixing wedge is oddly short and undecorated; See ballistas on stands in Payne-Gallwey’s book “The Crossbow”; bought from Terry Sovine (French name?) (address given but not shown here).
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David Martin wonders whether the bow has been put on back to front; there are two holes in the side of the frame towards the back which may be to fix the crossbow to a stand. (I disagree); when strung the string slopes downward from the centre; the screw thread on the screw holding the trigger spring is approximately
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1BA and the thread on the animal-like sight is 2BA- both are a bit sloppy so I have locked them with Araldite; the barrel wobbles up and down a little; the sight centres ones aim but is no help for trajectory; there are file marks inside the outer wings and the centre ‘window’; catgut loose on right hand claw.