I have a little personal experience with some of the later guns.  An uncle was fond of them and had one in 20 gauge and one in 12 gauge.  I got to shoot both as a young man and while they are really well made guns I never found either of them to be comfortable for me to shoot.  I think it was primarily a poor fit between me and the guns as Winchester sold something like 2 million of them over the production life.

On the 20 gauge, if it is really an early gun it would have been fitted with a 2 1/2" chamber from the factory.  That was the standard shell length back then and if it has a 2 3/4" chamber it has either been modified at some point or rebarreled if it has the more modern 2 3/4" chamber.   A lot of the older guns were modified as the industry switched over to the longer shell standard but if it has been modified or rebarreled its not worth as much as an early, unmodified gun would be regardless its condition otherwise.  Refinishing the wood might make the guns more esthetically pleasing to look at but if you're interested in collector value I'd probably leave them alone.  If they are shooter grade guns and destined to be shooters going forward suit yourself. 

Prices on the model 12 are all over the map depending on what it is, when it was made and the condition of the gun.  Seems like even some of the ratty looking old guns of questionable lineage are bringing several hundred dollars though.  The owner is probably not too far off the mark for guns that are in "VERY GOOD" condition but it doesn't sound like either of these two really qualifies in that regard. 

Hope that helps a little.  Maybe somebody else can weigh in and give you more to go on. 

No I looked it up it is 30,xxx.  First year, 1912, production ended at 5800, second year ended at 32,418.  They built number 1,000,000 in 1946.  1,964,384 when mass production ended in 1963.  Special editions and limited production continued until 2006 giving it 95 years in production.  I have not found total numbers, but it looks like 2,027,000 and change were made by 1980. 

Late to the thread.  I do have a soft spot for Model 12 shotguns, but not so much the very old ones.  I'd rather have one made in the 40's through late 50's.

The only Model 12 I currently own is a mid 50's 12 gauge 3" magnum "Heavy Duck Gun".  It is completely original and in about NRA 90% or so condition.  It's a beautiful example, with the more desirable solid rib.  All I've ever done to it is rub a little boiled linseed wood into the wood.  I've owned this one since the mid 1970's.  This was the epitome of the duck/goose blind gun of its era. Super tight full choke pattern.

They could be fired very rapidly for a pump.  If you hold the trigger down, it will fire every time the slide is pushed all the way forward and the bolt returns to battery.  That's not the most accurate way to shoot one, and not advised for shooting fowl at longish range, but it is fun.

Good examples that have not been worn out or modified are hard to come by, but worth looking for.

Forgive poor photography.

Our model 12 has worn bluing and some sort of twisty choke on the end  .

Is it one of the old "Polychoke" units?   

Yes! That's the one  .

It's not lowballing if that is all it's worth to you.  The owner can either accept your offer or look for someone who places a higher value on the item.
One of the reasons I have quit going to local gunshows is all the morons with vastly over inflated ideas of what their stuff is worth.

I liked the feel of the model 1912 action, I liked the history, I just already have three shotguns I don't shoot.  The real worth to me was more than what I could afford to pay, and more than the market value.  That is why I said it was a lowball.