when you say you found it on the cylinder shell but the port is blocked? where at on the cylinder shell did you find it? Was it near the top of the shell where the gland nut screws on?
How close to the top?
if it was within a couple inches from the top then that may be a set screw and not a bleed port, some of these old cylinders had set screws that were designed to hold the packing nut in place so it couldn't back out.
Usually if there is a bleeder in the shell it will be several inches down from the top of the cylinder shell but in most cases it is in the top of the ram.

I am going down toward the shop tomorrow, i'll look around and see if they happen to have any old manuals there for this model.
If they do i'll **** it up and scan the parts page diagram for you.