After a LOT of work, & trial-&-error, I got it to this... (I've done more since I took this, it looks better now - & the worn area in doorway has been filled in w/finish from surrounding area).

Scrubbing (diluted Simple Green, don't know if it was best choice, but seemed to work ok) got the drywall mud & 80+ years of grime off, the paint splatters took a lot more of scraping & rubbing. (1 thing I learned - an old credit card is easier to use & kinder to the wood & existing finish than a metal paint scraper). I actually like the worn "path" where others have walked for so long, & don't want to alter the actual finish until the other 2 rooms can be done also. (They're contiguous, so I want them to blend together). All I've done is rub a lot with denatured alcohol, it seemed to slightly dissolve the finish & allow me to spread it to the bare areas. Then it hardened back up & got shiny again. (Still don't know what the finish is, exactly). 

One of my questions, how to deal with the transition in both doorways, where the carpet was cut. I want it to be temporary, & I'd hate to put a bunch of nails or staples in the floor - I just removed a thousand of each from this floor!  Any thoughts?  Lol, duct tape comes in fashionable colors these days, right?? 
I don't suppose anyone can tell what kind of wood it is, from these pictures?  I'm guessing either Douglas fir or yellow pine.  There is some splintering, I'll be asking about that next, lol - but the wood itself is very hard. (trust me, I've been sitting on it for a couple of weeks... Pulling tacks & staples, (learned a few cool "tricks" for getting them out without scratching the floor! I'll be glad to share, if anyone is interested), etc. 

I'd guess some sort of soft wood too, but of course when it's on the floor of an old house, it's anything but soft.

Instead of duct tape, and only slightly nicer, how about that 3M double sided foam tape under a regular transition threshold? You're good at scraping already! :P

You can use carpet tape under the remaining carpet edge...it will hold until you get around to removing what's left.

Columbusguy, I've said before... Those staples lay eggs, I swear they do! You get them all pulled, then a week or so later they hatch & new ones pop up. You KNOW that one wasn't there yesterday!

My first mistake was when pulling up carpet pad, wasted so much time wrangling the left-behind pieces from under the staples. I eventually quit doing that, when I realized it actually protected the floor from the flat screwdriver I used to raise the staple enough to grip with pliers. (& makes staples easy to find, lol). For the ones without padding pieces - my first use of the credit card on this project. Well not really... First use was new washer/dryer to replace old one that caused all this, new bathroom subfloor, bamboo flooring (it was a compromise - DH got what he wanted in bathroom & I got to do what I wanted in this room. Refer to 1st pic - he was less than enthusiastic about my plan!).
Anyhow, I found that if you can wedge the corner of plastic card under the staple, then - w/a very thin head screwdriver, you can dig & pry the staple up. Cutting an old card helped, made it possible to get it further under staple. Also helps, if you can, to pry from the other side of staple toward the "bulk" of plastic - in case you slip! (& you will @ least once if you're anything like me, lol).

So... I know it sounds like a silly idea, a lot of work, & slow - but it worked great for me. After a couple of the little buggers are up, you find a rhythm, & it goes really fast. I kept pliers & magnetic bowl with me, & left the card in place to yank the staple out. "Card in left hand, pry from right, grab & yank, next! Not having to be as careful about scratching finish made it easy to go quickly!

I can almost guarantee at least one cut from doing the prying. :) The wood is some sort of pine, but don't know what--it splinters at the edges, but has really great patina; since it was laid in 1908, is there a chance of it being heart pine in Ohio?

The fact that alcohol dissolved the finish tells you that at least the top layer is shellac. That's good because you can easily touch it up - unlike poly. You could also put a layer of paste wax on it as extra protection. Though if there's poly in your future, paste wax is a no-no since it might interfere with perfect adhesion in the tiny cracks between boards.

Shellac will mark with water, but again, easy to repair.

I, too, find old credit cards the nuts for floor scraping. I was totally bummed when the unsolicited ones that arrived in my mail box began to be just cardboard facsimiles. I never miss a chance to scarf up a plastic ID card/old credit card.

For the margin of unfinished floor near the carpet, I'd think I'd fiddle around with more shellac or alcohol to get a big of surface protection on it (and issolve the ridge)and then leave it until later. Duct tape is not a bad solution. I have a place where I have dropped in a carefully fitted piece where two flooring surfaces don't quite meet. Double stick tape underneath it keeps it secure.

If you want to pretty-up your floor and you double check to make sure it is shellac, you could try another layer of it, with a rub down with steel wool afterward for a nice glow-y look. Test in closet to be sure you like it.

Shellac doesn't have too many fans these days because newer finishes like poly are easier to apply (mostly less labor- intensive, because it needs more coats, though they do dry in a flash), wear longer and modern floor guys have never worked with shellac. OTOH, shellac is a natural renewable material (it comes from bugs), with a long track record.

Shellac is what is on my kitchen fir floors. I do scrub it with water, but dry it fast so I have no appreciable spotting.

I like my wear patterns, too. Wouldn't want to erase 150 years of feet.

L

I'm glad you said that, about it being shellac. I was pretty sure, myself, & learning a little bit about it had me WANTING it to be shellac. Seriously cool stuff.

Regarding the thresholds... The one where bare wood (& embarrasing boxes of new bamboo hardwood flooring, lol) is visible, I'm not sure there. Can't see very far under carpet, but suspect that's actually where a wall was & floppers decided to put a door there. Where I think the doorway may have been is where they put a large closet - the only one in the house. The threshold to the left - into living room & out the front door (should one be so inclined - & I suspect that, at this point in my house-catastrophes, many would be!), it appears to be the same finish under all of those (presumably toxic) layers of flooring history. I will try to blend it into other doorway, but that wood is bare - it'll only go so far, lol.
I've looked at a few places for the flakes. (Generally found the wrong kind of "flake", lol, but they were just working there). Haven't tried menards yet, just opened here & I just haven't been. DH says to try there, thinks they'll have it. Anyone find the shellac flakes, in store not online?
No, there's a dedicated lack of poly in my floor's future. (The wood trunk I'm refinishing - different story, lol).
And "Thank You", for understanding about the wear patterns, & how I don't want to make my old floor look freshly-installed! I swear, every time I walk through that room - I get a warm fuzzy feeling. It's basically a hallway, can't go to bathroom without traveling "the path". (No WONDER it's plumb worn down, lol!!). :-)

I know this is an old thread, but I am interested in keeping a shellac floor in a bathroom and kitchen but am concerned about water spots. Did you wax on top of yours? If so, what did you use?