"The outlet is about an inch below the top ,brass securing ring on left hand side and configured so that the threaded internal port
is pointing down and parallel to the cylinder."

This sounds a lot like a bleed back port to me, they used to use them on old cylinders in case the packing inside had any bypass and fluid got on top of the ram inside... when the piston got to the top of the stroke it would allow the excess fluid to go back to the tank... which is what i was talking about earlier on some older lifts. They would have a return hose that went back to a port on the tank.
So definitely a manual would be very helpful.

i checked at our shop and did not find anything this old there... sorry about that...
Wish i would have found something...

Good luck