I should also say that it was obtained from a castle in Italy. It has a coat of arms near the breech end but it is not readily identifiable (I chatted with the good folks at the College of Heralds in the UK).
I am reasonably good at researching stuff but I have hit a wall (HA!) on this one. To find information on the object or references I have spoken to or otherwise communicated with the Met, the Wallace, the Royal Armouries, Robert Held, Ian Eaves, the NRA Museum, Flayderman, etc, etc. Zero, zip, bupkus.
There are a lot of examples of these things (Turin has a few and they were helpful..well, sorta) but there seems to be very little written. Even Held in his book "The Age of Firearms" tosses them off in a couple of paragraphs. Carpagna, in his opus "Bresican Firearms" barely makes a mention of them though I suspect that it was indeed made in Bresica.
I guess it is because they are sort of odd: Midway between cannon and hand held firearms.
The Director of the NRA museum put me onto the Mancuso book. He swore he saw it for sale at the Baltimore show. I spoke to the secretary of the Baltimore Gun Collectors Association and he actually looked at the list of exhibitors going back 5 years. No Mancuso, no Wall Gun exhibit. I called the NRA guy back and he swore he was right (and says his buddy was with him and remembers the same thing). I had fully 3 people at the latest show looking for spoor. Nada.
Flayderman, who is Godlike in his knowlege of everything about weapons and people knew nothing.
Incidentially, before you guys go crazy, the name "Mancuso" will seem familiar, right? It was to me too, and Flayderman and a half dozen other people. Know why? That was the name of the American Skipper in "Hunt for Red October".
Arrrrggggghhhhhhhhhhhhhhhhhhhh.
Perhaps you can now understand my frustration.