I know that there are some copies of hornbow crossbows; when I said I thought it could not be done I meant, properly done - just exacty the way it was done 500 years ago.
Yes, the two Churburg cranequins (images attached from the Churburg catalog) rank among the finest in existence, together with the Odescalchi cranequin, of course. Their gear boxes are all decorated with Gothic tracery, of brass I think.
As you can see on the earliest known dated cranequin, 1504, once in my collection and now it that of a friend, gear boxes are fixed by iron tacks until at least the 1530's, sometimes up to the mid-16th century. In some cases they are riveted, though.