The action has a large pin through at the front, much like
a double rifle with tilting barrels. The barrels have a
notch that hooks around the pin and they are locked in
place when the forend is latched. They do not tilt to
remove, they just slide back and up when unlatched. A
very difficult arrangement to build.
Herr Kersten was a world class gunmaker from the looks of
this example.
Raff