not real familure with what the B-78 is, but looks like an 1885 to me. Am I right? If so it's similar to a Hi-Wall. They made a gazillion versions of the Hi-Wall and Lo-Wall, and also different barrels and even a half octagon barrel (seen a couple).
I have a Hi-Wall in 38-55 with the flip up tang sight and the octagon barrel. The wood is satin finished and very nice furnature grade wood. Yours looks like the normal gloss finish. But have never seen one in 22-250. I have seen a couple in 25-06 that looked identical to what you have.
Value wise, I looked at a gently used 45-70 a couple months ago that was very similar to what you have, and I passed on it when they wanted $1000 (I'd have gone $850). Was going to rebarrel in in 40-65 if I had bought it.
I also have a .223 Lo-Wall, and it's kinda like a scaled down Hi-Wall clone (maybe 3/4 the size). Otherwise nearly identical. This rifle has been it's own nightmare from the get go, and it never was actually the gun itself! Odered in new bases and rings from Leupold (I wanted matching gloss rings and bases), and when they came in I put them inside the safe forgeting I even owned the Lo-Wall for several years. I look in my safe one afternoon and see two or three odd rifles on the back row left hand corner! Drag them out for a look see and there is this beautifull Lo-Wall and a MK. V. WBY in 30-06. Plus a commerative 39a with gold inlay and an octagon barrel!! The WBY and the 39A still had the hang tags on them!. Well I gotta get out and shoot this Lo-Wall, and found the bases and rings for it in the safe as well. Bought a mid line scope for it, and set the rifle up in the vise to work on it. The bases looked really nice, but Leupold sent the wrong screws for it (too short). Called them up and the guy at Leupold said they were correct. I told him that it was funny as they didn't work on either the front base or the rear. So he sends me screws that are about a half inch too long, and are the old style. Call him back and he hung up on me! I can make these screws work OK, but never enjoyed cutting off little bitty screws. Out of frustration las spring I called Burris and told them what I was looking for and they had exactly one set in the wharehouse (no longer produced). They gave them to me to get rid of them!!!! So if you need a set of bases you better stat looking. But if you don't mind matte bases, I'm your friend.