I have made three butcher block tables and getting the finished surface
flat is really a bear. I am guessing that it is made of end grain
maple and that is very difficult to get smooth if you were to try and
surface it with a router. I would recomend giving it a sanding and
then oil it with mineral oil. You don't have to sand it so deep that
you remove all the knife marks, probably hard to do anyway, and I doubt
you would take out all of the stains either. If you are going to use
it for food prep make sure it sees some bleach, then oil it with
mineral oil. Mineral oil is food safe, you will find it in the
drugstore with the laxatives and it will prevent the thing from
cracking.