The level is finally back together with an intact main vial (the other two were good and still are) and is calibrated.
I bought a 2 kg box of plaster of paris (POP) and have about 1.99999999 kg left
Any ideas for using the remainder are welcome.
I found some fairly thick (like poster paper) acid free white paper for backing and the vial still had a very small amount of room (diameter wise) with one layer of paper so that worked out well.
Transparent tape was used to temporarily hold the vial. The groves for the two circlip springs can be seen here:
I had several plastic drinking straws ready to cover the small "tit" on one end of the vial but found that I did not need to use them. Instead I applied POP in small amounts with a bamboo skewer and kept it away from the "tit". The other end was easier although I used the same method. I did 3 applications of POP to get both ends nicely anchored and was quite happy with the final result. The pointy end of the skewers was used to wedge the vial up towards the opening at the top. A very small amount of cleaning up was done at each end.
I put the two spring wires in place and with great difficulty finally managed to get the protective cover over them. This was likely the most difficult part of the process as they did not wish to sit in their respective groves.
Putting the plugs in each end was causing me a lot of headaches, trying to figure out how to keep them properly aligned. I have a surface plate along with a decently flat piece of glass and a pair of 123 blocks so checking them was easy. I was thinking of making a jig with the 123 blocks - basically bolting the plugs, one to each block and then pressing the blocks together on the surface plate. This idea was abandoned as too complex plus my larger clamps did not want to cooperate.
Finally I decided do the following:
1) press one end in as close as my eye would allow.
2) align the two plugs resting each on a 123 block on the glass.
3) squeeze them together as much as possible by hand while aligned on the blocks
4) do the final compression in my rather decent sized wood working vice checking the alignment regularly as I pressed them together.
I found that the plugs required a lot of pressure to press into the tube. Large C clamps and other types of clamp either could not provide enough pressure or were to wobbly to be effective. My large wood vice is lined on each side with plywood and the plugs ended up pressing into it without any damage. Here is a mock up with a piece of similar sized brass - I don't have photos of the tube in the vice.
And a final couple of photos with the level back in operation.