I decided to take the lufkin apart. It's a Lufkin no. 58 machinist's level - 12 in. long. The main vial is cracked and leaking and the collar rotates a little too easily.
Once the vial holder was off the body I held the flat on one end in a vice and turned the other end with a wrench - in case the end caps were threaded in. Apparently the 12 in. starrett equivalents are press fit but I didn't want to wreck it in case it was threaded. It turned however broke the vial glass (no loss) and the end cap didn't thread outwards. I made the assumption from this that it also was press fit. Being fully committed now I needed to come up with a simple puller.
A bit of thought and lunch and I came up with a jig to pull the end caps (one anyway) off. Not very high tech but it did work without breaking anything and was very controlable. I first turned down some 5/16 in. drill rod so that the holes in the caps just fit the rod. Two pieces were made. In the photo below the drill rod holders are not inside the screw clamps:
The drill rod fit like so:
It isn't fancy but did hold quite well inside the clamps once they were tightened up.
I used 3/8 in. threaded rod and gradually used the two nuts to push the blocks of wood away from each other. The nuts are the ones on the left side of the second photo. It took a considerable amount of force before the plug started to move but was easy after that. The drill rod bent a bit before the plug came out.
Once the one end plug was removed the outside barrel slipped off revealing two very fine wires in a groove at each end of the vial holder. They are supposed to prevent the outside barrel from spinning easily - giving a little bit of friction to hold it in position. Not sure if a little judicial bending will improve the friction or not.