Things that drive the value up...
1. If the revolver and contents of the case are highly polished and the interior of the case is completely free of dust, the eye appeal goes up.
2. A cased set has appeal which might be slightly higher than the value of the individual items minus depreciation (maybe ten percent). Not much but some. If it isn't well maintained (dirty, dusty, lint in the case, not polished up)that is not true.
3. If you find someone who wants your specific item that buyer may be willing to pay more just to get it because it is not something you see every day.
This is an item which does not enjoy general popularity. The size of the market is small with respect to the overall firearm market. Black powder shooters and more specifically cap and ball revolver collectors are not as numerous as other market descriptors.
If the market were large, you could put the item on Gunbroker and just wait for the masses to establish the value with their bids. But since the market is small, (perhaps as small as one interested party) you might find yourself giving it away since there is no competition among the buyers.
If you have a little time, you could list it on Gunbroker for a high price with reasonable shipping (15.00 for Priority and of course no FFL requirement) If it is a brass frame revolver, list it for $300.00. List it for five days because, since the market is small, the visitors to the listing is also small, You want at least five days to get good market penetration. If it doesn't sell, drop the price by $25.00 and list it again. Keep dropping the price until it sells or until it gets so low, you just feel you should keep it.
One personal note. When I see a reserve price auction, my reaction is the the seller is trying to play fast and loose. I like it when a seller, lists the initial bid as the lowest price he is willing to accept, and sets a reasonable shipping cost. A Walker Colt can be shipped anywhere in the U.S. to arrive in 2 days for under 12 bucks.
My reading of history convinces me that most bad government results from too much government. Thomas Jefferson