Hi Fernando,
A most interesting lock indeed. Nothing in any of my books remotely like it!
The Lazzaro signing is in my opinion DEFINATELY false. Any guns by this maker I have seen are signed in flowing style and gold filled! This looks to me like punched letters.
Those marks on the barrel could POSSIBLY be British, but lack of clarity means that positive identification is impossible.
General overall style could also be British (but equally Continental European), but the ramrod looks definately odd!
Sorry I can't be of more help.
Regards Stuart