Only loading the #8 for fun, wall guns were usually military and shoot ball. This one is a civilian gun, has the military lock but no ordnance acceptance mark. I think it was probably mounted on the hand rail of a tall ship out on the spice routes, they'd take a wall gun if they couldn't justify a cannon.
It dates from about 1790, has the name MEWIS on the tang but whether they made the tang, the barrel or the whole thing I don't know. A Birmingham based company, usually military rather than sporting.
Everything on this one is scaled up unlike the military version which had a normal sized trigger and guard. Trigger pull is around 25 pounds because they scaled up the sear spring to ::