Yes, you see Thru!
It's possible to watch Bendix Economat collapsing the tub .
There's a 'tool' used to measure the pressure of tub that can be attached to the top of it with the lid open. This tool looks like a round tray with a manometer in the middle and it's transparent.( And I can tell you : It's not so cool to watch it, once the rubber 'sticks' to the trasparent surface and it's not possible to see the underneath it)
I think I still have one of these transparent trays. If I happen to find it I'll take a pic of this tool. I have had two Economats but they've gone away a long ago, otherwise I could film the tub collapsing .