Antique Mirror

I have a mirror from my great aunt (no longer living) that I'd love to figure out how old it is and what the wood is. The mirror is full-length (26.5" w x 58.5" l), framed in a heavy (and I mean heavy!) wood. I'm wondering if it is walnut--maybe mahogany? I think it may have been part of a dressing table because it has small dowels on the sides. They aren't large enough to fully support the weight like a mirror on a stand. I got it from my great aunt back in the 70's and best I could tell it had been around for several decades before that. Can you can tell from the style? What's a good way to figure a value on this? I wish I had asked more questions, but I was too young to think about that. Thanks!