Well I guess I don't have an African trade gun lock, cause mine doesn't look like that.
On mine, the lock plate is made in two pieces. The rear part has the hammer and its internal works, and the forward part has the pan, frizzen and spring,,,, and the two parts are made is such a way that a single screw holds them together.
I guess it was the screw between the hammer and pan on the double rifle shown that caught my eye. I don't really know what the pan, frizzen and spring on mine should look like as those parts are missing.
I'd post a picture, but I'm out at sea and the lock is at home.
John