If your house is a kit it should have letters or numbers on the structural pieces. Kits were often number or lettered to help in the construction process.
Take a really good flashlight down to your basement and have a look around on the beams. You might surprise yourself as to what you will find.

Not all kit homes were numbered.

On the other hand, you'll often structural frames from very old houses with numbered members (indicating they were likely built, assembled for checking fit, then knocked down and reassemebled on site. They are usually marked with Roman numerals (easy to mark with a chisel).

The brand-new kit houses from IKEA have numbered pieces.

Wow, IKEA has kit houses?

I've noticed on the back of our hinges there is an "S" stamped into the metal. The metal is a copper and black finish, nothing fancy.

Hmm, maybe I'll start a Sear's Kit thread...

From what I've heard, experts spend a great deal of time dashing the hopes of people who think they have Sears houses.
I recall the smoking gun is there should be a packing label under the main staircase, or remnants of one.
Whatever it turns out to be, it looks like you're enjoying it!

Dawn,

Didn't you say before that you thought your floors were fir, not pine? That's what they look like to me, at least the picture with the white paint blobs.

Before I'd sand the floors, I'd try a variety of clean-up/ strip off test areas to see how the floors look without going down beyond removing the current finish (by stripping alone or in combination with a very light hand sanding). It might surprise you, how nice it could look. Do not put down any trial finishes on the test areas once they are clean. The areas may still look quite dull, though, without any remaining finish. To see how a the floor might look with a finish on it, you can try a quick wiped-on coat of mineral spirits or paint thinners. BE VERY CAREFUL WHEN DOING THIS (if using solvent to get a quick test look) as you are creating a flammable condition and the floor and any rags used will be at risk of fire until it is all safely evaporated. Use lots of ventilation (fans to outside are good) and dispose of any rags/paper towels used in solvent test clean-up sealed in water-filled metal cans, for safety's sake.

If you clean off a test square yard or so, you'll get a good idea of how your floor might look (vis a vis condition issues like dings, scratches, etc.) if you just have the current finish removed (along with any surface dirt, drips, etc.) The real test is in areas where you might have stains from water or other liquids that have penetrated whatever finish is on now. Those stains might be so deep and obtrusive that you might want to sand them down to make them disappear. The downside there (aside from loosing the overall patina) is that some may be so deep you can't sand them out anyway. There are ways to improve water stains using acids and bleaches, but they are not always successful. You could also, for a small area, remove a piece of the floor board and make a repair using a Dutchman to eliminate a really deep stain.

I didn't see any cracks worth packing or filling.

One other negative thing about sanding down the floor, you may still have darker lines along the edges of the floor boards that will be more annoyingly visible if the surface of the boards is sanded down to lighter, un-age-darkened wood. There is no way to get the cracks completely lightened up.

Do you know what your floors are finished with, now? The options (for older materials) are varnish (most likely) or shellac. You can separate the two by seeing which one is alcohol soluble. (You can use any kind of alcohol from Stoli to rubbing alcohol, but probably not beer.) Shellac is alcohol soluble, varnish is not. You will be able to feel the disolving of shellac by the alcohol, because the wipe or rag will get a little tacky.

Meanwhile, if your floors seem too grungy to live with you can scrub them if you are careful to get any water you use back up quickly. I use hot water and liquid dish detergent, not Murphy's Oil soap which can leave a residue, with a stiff scrub brush and a couple of bushels of machine washable cleaning rags and drying cloths. A much better solution is to use a powerful steam cleaner like a Ladybug or TidyVap. These are pricey, but I have found mine outstanding for heavy duty remodeling-type cleaning. I find most of the other uses posited for steam cleaners to be overblown, though. Perhaps you can borrow one from somebody to give it a try. The benefit of the steam cleaner is that it is much dryer than the scrub-and-wipe method; virtually no moisture is left on the surface. Also hot steam is great for removing grease.

You certainly seem excited and energetic in learning about your neat old house and how to bring it back to it's former glory. Good luck with your projects, just remember you don't have to get it all done at once. Be sure to plan for plenty of non-work periods, so you can enjoy your house, and enjoy your life in it. (Perpetual remodeling can be hard on a marriage!)
Molly~