Hello Rob,
Interesting little dagger you have there, I guess that it will be a challenge to restore it. Frankly said I am not familiar with the term "Italian vendetta" dagger but with the term Corsican vendetta dagger but these looks a little bit different, see for example here:
http://www.vikingsword.com/vb/showth...light=Corsican
But I would guess that your one belongs to the same family of daggers. Could be Corsican but could also be Italian.
Attached is a Corsican one from my own collection, it's 23,5 cm long inside scabbard.
Regards,
Detlef