The barrels are held on by one screw through a slot.
Turning the handle rotates a cam which engages the underside of the barrels and pushes them back and forwards.
Once the barrels have moved far enough forward that they disengage from the rod they can drop down on the slot.
Opening the gun automatically cocks the firing mechanism. The ‘bolt’, if that is the correct term, protrudes from the back of the action and acts as a cocking indicator. The two lugs you see here can be drawn back and rotated locking the bolts and acting as safety catches. I am not sure how the cocking mechanism operates but it looks like the bolts work in a similar way to a rifle bolt but without the handle. The trigger pulls were very crisp.
The firing needle can be seen here, partially withdrawn as the breech is opened.
The hand grip and trigger guard seem to have been made out of some kind of horn.
