Apparently Friedrich Jung, Suhl, combined the Teschner/Collath breech action with the triggerplate lockwork of the Feist, Meffert “Hubertus Safety Gun". Here is a photo of my “Hubertus” double lockwork, uncocked and on “Safe”.

It works this way: The hammers are brought back to the full cock position by moving the opening lever under the foreend. To put the gun on “fire”, you press the grip lever up until it is caught by the catch behind. This puts tension on the mainspring. Now the gun works like any other hammerless. Opening the breech recocks the lock and you may continue shooting without further movements.
To put the gun on “safe” you release the catch behind the grip lever. The lever snaps down, relieving the tension of the main spring. This also activates a slide on the triggerplate, blocking the sear and rebounding the hammer off the firing pin. Now the gun may be carried fully loaded, but without tension of the mainspring and with all other lockparts blocked. The barrel selector switch of this drilling is a slide on the top strap like as on most conventional drillings.