Part of stairs that weren't finished by the previous owner for unknown reasons. I want to finish to match, but not sure if I am supposed to use a wood stain, varnish, or if I can use a polyurethane clear gloss coat.
Picture with flash
and a view of the other side that they did finish (without flash)
Is this a stain (maybe dark walnut?) or some other type of finish? What should I get to have the closest match?