Rob,
I don't have a clue what type of wood the knobs are made from. I would ask Victor or Joseph on this. My knobs are medium dark, similar to your description. They are nice looking, but I wish they had a marking that you could see easier to know where your volume is set, but I don't complain as I go by the volume that sounds best to me anyway. Let us know what the wood is made of if there are no posts made about them.