I'm glad you like it.
I couldn't find out a lot about this. Used by the Japanese on the siege of Port Arthur during the Russo-Japanese War at the turn of the 20th century. The Italians used a very similar gun in World War One. I found conflicting info as to who exactly designed this gun - the Japanese or the Italians. In any event the Japanese also appear to have used this gun in World War One where some were captured by the Germans and also into World War Two.
Check out these links for more info and pictures:
missing-lynx Braille forum thread