Vacuum variable cap

[WU8V]

I have a vacuum variable capacitor that looks incomplete... hopefully, these pics will show what I am trying to explain, and someone will know the story behind this thing... thanks   WU8V

As you can see in the end photo, there is a cavity that I believe there should be some sort of slug or something?

The bracket is some sort of phenolic material and there is a rubber grommet type thing at the "hole" end

Specs...325-505 pF  20KV  60A

[w4bfs]

In other vac varys I have seen, a threaded 'puller' goes inda hole and engages the movable part .... I really can't tell from the picture but this type may require an expandable collet (sort of like a pop rivet) to engage ... looks like newer stuff ..73