Jani is almost certainly correct about the hammer gun having originally been a two barrel set. It is a very elegant gun. The boxlock is a fairly typical, good quality, double of the period. Because the Austrian cities largely avoided the attentions of the 8th Air Force and British Bomber Command, there is some chance that you may find out something about these guns.
Both look to have been well cared for by your father. Having spent 29 years in the Army, I can attest to it being a fairly compulsive behavior pattern! You should get into shooting them. Suspect they are both fairly tightly choked, but one never knows until a guage is run through them. Either would be fun on a clays course, and that hammer gun would be a particularly elegant companion for a "girl" architect.
A lot of us can get a bit spiritual about such guns, and taking them out would not be a bad way to spend some time with your father.
