Got a buddy with a recently purchased (secondhand) later production American 20" lathe with the 27 speed headstock (think it says 'Model B') that has apron mounted leadscrew reverse. Upon attempting to help a younger guy learn to cut some LH threads today, I discovered that the leadscrew reverse isn't working. The leadscrew works fine in the lower clutch (RH) position, and pulling the clutch up to mid position shifts the leadscrew drive to neutral, but pulling further up does not reverse the leadscrew. We made sure to only try under 200 RPM since there's a data plate warning about that on the machine. We pulled a couple covers off to investigate a little but there isn't much of consequence visible. We were able to see that there is a shift fork with what appears to be a thrust bearing operated by the reversing lever and what is visible seems to be functioning correctly, but whatever the shift fork is manipulating is buried deep inside the lower part of the headstock and not visible without further disassembly. Anybody familiar with these and maybe been through this before and have an idea what may be going on? I'm starting to think someone disregarded that 200 RPM warning at some point and slammed reverse at high speed and damaged something.