A little more research in another one of my books says it was made in 1882.
Your gun is what is called a THIRD MODEL or last model made.
This is noted by the dust cover on top of the frame as having the slide rails made as part of the frame itself instead of the early version having the rails installed separately.
It is also noted that the third model only had one screw located at the lower rear side of the frame in stead of the earlier two screws just behind the side plate.
Your gun has a few special order features on it.
1-It has an octagon barrel, round barrels were standard but most guns were ordered with octagon barrel.
2-It has a 2/3 rds magazine. This is a quite rare feature.
Most all rifles had a full length magazine while some had a half magazine.
You don't say what length barrel your has.
That can make a difference also.
Also need to see a pic of the front & rear sight along with a pic of the trigger.
If there is a small screw beside the trigger than it has a set trigger. Again, this would be special order.
Your gun has the standard rifle trapdoor butt plate. Shame it doesn't still have the cleaning rod with it.
The wood looks to be of standard grade Walnut with a good percentage of finish but would need to see it first hand to say for sure.
From the pics I would put this gun in about 50% condition. Really hard to say without seeing it first hand.
Blue Book OF Gun Values #29 which is a couple of years old lists it as having a value of about $1500.00 to $2000.00 for an above average gun, which yours is for sure.
One in the 50% range as about $2700.00.
To this it says add 20% for caliber 44-40 in a third model.
It also says to add 30% for an octagon barrel in caliber 44-40 only.
In my experience this seems to be a little high since most of the guns you will see are of octagon barrel configuration, but that is what the book says!
According to the book, you are now over $4000.00.
Then you have to add for the 2/3 rds magazine along with anything else that it might have that we have not seen yet.
Could add several hundred dollars to the right collector.
It can all add up rather quickly.
Of course that is retail book value.
In reality you should expect at least 1/3 to 1/2 less if you are selling it to a dealer.
All in all, you have a very nice special order third model 1873 Winchester rifle.
I have seen enough to say that I would definitely invest in a factory letter from the BUFFALO BILL HISTORICAL CENTER - CODY MUSEUM --- CODY WYOMING regardless of the cost.
It would only enhance the price considerably, provided the factory letter backs up and confirms all the features that the gun has!!!
It could prove that some things have been changed or added also?
That is the chance you take.
Winchesters are so highly collectable that there have been a lot of fakes or enhanced guns put out for people who really don't know what they are buying!!!
Please take it to a very knowledgeable gun appraiser that specializes in lever action Winchesters and pay him for an honest appraisal.
By honest I mean ask him what percentage of his appraised value he would be willing to give for the gun after he has given a written appraisal..
If it is in the 70% range then most likely he is honest.
That should work out to about $2700.00 or a little better.
After all, he has to make a profit on it too!
I have found this to be a good honest average over the years I have been a collector.
Please keep us up to date as to anything you may find out about this gun.
LONGTOM