Most all leaks on the control valve side of the rockshaft is the result of plugged leak-off tubing and/or piston seal leakage in excess of tubing capacity.
The vent-leak off tubing conveys piston seal leak-bye back to the torque tube. If the tube is plugged or the leak-bye is beyond the capacity of the tubing, oil level rises in the rockshaft housing and leaks out the control valve side which has no seal or gasket.
To measure piston seal leakage, pull the vent-leak off tubing off at the fitting. Cycle the hitch up and down about 10 times to void the collected oil in the rockshaft housing. Put the draft arms up with some weight. You should be down to a slow, intermittent drip or the piston seal needs changed.
1953 VAC should have 2 O-rings for piston seals unless it has been changed back to the older leather cup piston. Very easy fix if that is the problem.