Those are very nice rifles, but no fun off the bench!
The B78s are slightly less desirable than the later 1885s because the trigger was improved on the newer ones.
I would guess $1000 would be a good starting point, but suggest you check comparables on Gunbroker; actual bids and selling prices, not asking prices. A lot depends on how you plan to sell it. Listing it online and willing to be a little patient will likely yield the greatest return, but can be a hassle. Advertising it locally will limit its exposure and may also be a hassle, according to my experience.
A dealer will probably only give 75% of the book retail value, if that, but would certainly be quick.
