Welcome to the forum.
Finish loss will hurt collector value. Overzealous cleaning ie: steel wool, sandpaper etc. will destroy it and render it into the shooter category. Collectors tend to pay more as unmolested 100 year old guns in pristine shape don't come around often. Shooters are just looking for something that goes bang and since there are millions of guns out there don't usually pay a premium.
Add a box, tools and original paperwork to a pristine gun and the price can rise dramatically.
The older guns have a smaller audience as most of the younger buyers are looking for black plastic tacticool guns.
Since many of these older guns saw black powder, which is very corrosive if not cleaned right after shooting, their condition tends to be even worse than their more recent smokeless powder brothers.
As gmborkovic stated, value is probably in the $200-$300 range but without seeing the gun close up it is always hard to give exact estimates.
If you plan to further clean the gun, do it gently with lots of oil and a cloth. A fingernail can sometimes remove built up crud or even rust without killing the finish. Removing the stocks and soaking the gun in Kroil or some other crud buster will also do wonders for the inner workings. You can also pull off the side plate and clean and lubricate it that way but care must be taken so that the screw and plate are not damaged. Buggered screws and pry marks will also lower value.
I hope this helps.