Well, I had an aunt who was disabled who got hooked on the shopping channel.
Sitting here in my wheelchair for the last 11 months, I understand, but for me it's gun auctions.
Just hours ago I won what appears to be a Ballard takedown with 4 barrels, two or 3 of which are Darr.
Caliber is just listed as 38.
The takedown system is crude and may not be Darr innovation, looks like a 44 but with the locking screw on the side of the receiver, not the bottom.
It seems to have started life as a Pacific and the original barrel/forearm are included. 
The barrel on the receiver is marked "G.F. de Vaudreuil".
The rifle also come with a palm rest and two ammo cans full of reloading stuff which are not pictured in the auction. I'm hoping for the rest of the tang sight and some other cool stuff

Setscrew on the side makes a lot of sense. The old gunsmiths put it on the bottom, right through the serial number, so the side avoids that. And a good machinist/gunsmith could make that setscrew also function as a post to hook a breech seater tool on too!

it seems his fav on this rifle is the 40-60 Bresien barrel, lots of his notes, some bullets and brass came with the gun.