I doubt the piece in picture is 100 years old simply because of wide growth rings. If the material is indeed 100 years old,,and,,,the choice is SYP and Doug Fir,it's SYP east of the Rockys and Doug Fir in Pacific NW. Without any clues,it look's to be pine. The good news is it can easily be matched at most any lumber yard.

Thanks- This is a Montana home so probably Doug then. I don't know when the wood was put in

Yes,out of the two choices you listed,Doug is by far more likely but taking it one step farther,ask locals about regional species harvested for construction. If you put more wood next to existing, stain might be more challenging than wood. If you are pulling any of the existing wood down for the upcoming project,I'd pop it off now to expose unstained back side. An experienced person can better id it while looking at unstained wood in hand. At minimum you should get scrap lumber and test some stains. Be informed that stain color changes somewhat when clear is applied. To get a fair idea how stain will look under clear,dap dry stain with saliva moistened finger tip.

Do you have some closeups of some of the other wood sections?

Kudz I wouldn't bet the farm on the species but I don't think it will matter much to a finish carpenter when it come's to blending new with old.

Agreed... :-)

So what type of wood would this be then?

"So what type of wood would this be then?"

Rather than asking people to guess based on a fuzzy picture,ask the person who recently bought and put it up. Here's a fact. Lumber wholesalers openly admit any given stack of material might be 2 or more species eventhough sold as one species. If forestery experts think they are similar enough not to matter,why should non-experts debate which is what?

tom-

My first guess is pine: Pine

Is this located in the South or Southeast?

South east Montana

I'm still inclined to say Pine as it doesn't look reddish enough to be Douglas Fir. Is this in your home?

Yes it is - the original pics with the finished wood

Our 1908 floors have wide growth rings.

You can't always judge growth ring width by surface appearance as the way it was milled (i.e., the orientation of the rings to the saw blade) affects the appearance. Sometimes you can only judge by looking at the board end-on to actually view the rings in cross-section. Take a look at the "Pine" hotlink I included in another post above to see the variation.