I have a CPA rifle butt stock that I would like to finish, as much as possible, like the original Stevens stocks.
Does anyone have an idea of what the Stevens company might have used on their rifles?

Talk to Paul Shuttleworth.

Most of the old original Stevens I've owned had a pretty shiny finish. I see a lot of them with satin finishes, but I always figured they were refinished. 
Many old gun makers used a oil finish, but started out with a dip in varnish to seal the raw wood first, and this sped up the oil finish process a lot.
I've gotten best results with Minn Wax Wipe On Poly, which I started using when Permalyn Sealer got too expensive. It gives a wonderful finish, that's durable, and easy to touch up if damaged. It also can be gradually built up, so you can watch it as you apply coats, and stop when it reaches the level of sheen you want to achieve. It comes in gloss or satin also, so getting the perfect look is easy.

How are you guys applying the Minwax?  Brush, hand, wax??

    The appearance of a stock finish film has a lot to do with its refractive index, and how it matches the refractive index of the wood fiber cellulose.   Tru-Oil is similar to a real linseed oil finish or a high-oil varnish (which is a good match to the wood), while the polyurethanes are not.   As a result the polyurethane lacks the appearance of depth that you get with the oils.  You can get a nice polish, either shiny or matte, but it still looks kind of "flat".

CHRIS
RGChristensen

Oil-based polyurethane sticks just fine to linseed oil w/o sanding.  (Avoid the water soluable Varathane.)

I refinished the Douglas Fir floors in my house by sanding them to bare wood, applying a really wet coat of Watco's Danish Oil Finish (essentially linseed oil with some dryers and other stuff) and then laid the poly right on top.

Eight years later and the floors still look fine.  The finish has never peeled or worn through.

Should be just fine on a gunstock.

I apply Wipe On Poly with a brush on new stocks, as it will really soak in the first few coats, and needs plenty of saturation. But I've also applied it with just an old T shirt, and it works equally well. I make sure I wipe off any excess after it's set for a few minutes, as excess will increase drying time between applications.
I wet sand with WOP between coats, which eliminates the raised feathers in the grain. Normally on new wood I do between 8-12 coats, but I do two a day. One in the morning, and another before bed. 
WOP will cover almost any existing finish, without reaction. But I always apply a small area as a test, and check it later in the day to see if it might stay tacky. If it's dried, then I proceed as usual.
I have used it touch up repairs I make in stocks, and it works great to blend existing finishes in after repair. Unlike other poly finishes, WOP can be easily repaired if it gets dinged or scratched, and not have to strip the whole stock to do so. It's as good as my favorite old Laurel Mountain Permalyn Sealer, but a bunch cheaper.