NU-PORCE
Glad to see that you took the tub back and cylinder off.I see that there are some rust issues in the tub.This is due to the water that was standing in the tub for who knows how long.The best way to deal with this is clean it perfectly,take it outside use Brillo pads.Rinse good with garden hose.Now for the rust.A wire brush will work well.Get it as clean as you can.With rubbing alcohol and a rag clean those areas again.You can get Nu-Porce at a hardware store or on line.It comes in 2 small bottles you mix together.This works well.I had a few small areas to touch up on my 58 15 some years ago.And when I changed the bearings on it a while back the touch ups looked like I did them yesterday.Hope it is just surface rust in those areas as those are huge pressure points on that machine.And the bearing seal did not leak at one time, it leaked the last time.Bearings in this machine are more than likely original.I would bet this is not a repair that was common in the 50s.The machine just got shoved in the corner of the basement where we are finding them today.As long as you have the machine apart you may as well go all the way with it.I can give you the info if you want to replace these parts.I would do it.