Although a 'dealer', I suffer from the same problem as most vintage gun nuts and that is enthusiasm for lovely old things.
As a result I ascribe a considerable value to an 'original' case or, more correctly, a case that is a good fit and carries the right labels.
A really nicely relined case or excellent condition original lined case I would value at between $800 and $1800 and although I might not add that full amount onto a gun that was being sold with it, I would certainly price the gun at between $500 and $1500 more than one without a case.
Of course, where the case is not highly specific to that gun, the purchaser may well be offered the gun (or case) without the other.
Accessories, named or unnamed, and labels are often sold for quite high prices to collectors who are 'making up a set'. This bugs the hell out of guys like me who are trying hard to put together a gun with appropriate case etc. but that's the antiques market for you!
I reckon to sell a nice antique ebony cleaning rod for about $120-150, oil bottles from $120-200, snapcaps from about $75-150. This all depends on condition, name etc.
Accessories with a cased gun don't seem to increase its value, just the speed with which it may sell!
