Hi, I am going to try to build a vanity to match this old cabinet in our bathroom. is it pine? what's your best guess on stain?
To me, it looks like rotary-cut pine plywood.
It looks to me like a clear varnish or poly finish over pine. Take the door off and take it to your local paint store for their opinion.
Keep in mind that pine will change colors as it ages (as do most woods), getting darker with time. So new wood with the same finish won't match the old for at least a year.