That’s a true boxlock drilling, not an usual Blitz- = trigger plate locks one. Such Anson = boxloxk drillings are quite rare, as they were more difficult to make than even a sidelock drilling. If you care to look closely, you will notice the underlumps of the barrels and the recesses in the action bar are offset slightly to the left. This was done to provide space for two locks, right shot and rifle, on the right side and one, left shot, on the left while still providing a slim profile. The main advantages of an Anson- over a Blitzdrilling are: The distance from breechface to triggers is about 1” shorter. This makes the gun less muzzle heavy, providing for better balance. The stock is much stronger, as the head of a Blitzdrilling is hollowed out much more to accommodate for the lockwork above the trriggerplate. As such true boxlock drillings were difficult to make and fit, they are even more rare than sidelock drillings. So less than 1% of all drillings are of true Boxlock-/Anson design.When you have it in hand, send photos of a marks under barrels, on watertable and on breechface. Maybe we can identify the Suhl maker?