Very fine steel wool.... "0000". Homer's furniture refinisher, in a dark walnut color.
Using the steel wool, apply the Homer's, rubbing with the grain of the wood. You may have to repeat it several times, wiping the wood dry each time.
When it's looking the way you want it to, finish up with Homer's Beeswax and Orange oil...following the directions.
Don't sand the veneer. veneer is so thin that it's easy to wear completely through it.
That's a beautiful machine!