At the risk of opening myself up to massive ridicule.
Does the "back gear" or low speed gear on your typical manual knee mill turn in the reverse direction of the high speed gear? I've heard the term back gear many times. Is that what it means?
I was just getting ready to try some chucked up power tapping on the new South Bend 10x54 (SB1028F), and the spindle spun in reverse of the direction indicated on the control panel in the lower gear. It spins the direction indicated in the higher gear.
I've never owned a real full on full feature knee mill before. The Hurco KMB1 doesn't count because it does what the VFD tells it to do.
I can write G-code for simple jobs at the control panel, but I don't know all that much about this manual machine.