OPPS!!!
That's what I get for not remembering my geography! In any case (!), NOT Belgian naval piece. As I have never really heard of the Belgian navy, just the sheer amount of these pistol-types is a statement as to the obvious exports of said item.
Now, a recap please of all known nations that actually used this type for their merchant ships? England we know for sure. France as well. Any Norwegian/Danish? They were certainly involved during the Napoleonic period.