Logically, the mystery-knob part is the oil-filter screen thingy. As they used other parts from the V8 kit on the Hoth Blaster. Its not written in stone of course, and with all the kits they had available, they could have used some other part.. but since they already made castings of the parts from the V8 kit - why would they use something else. ?
Ive now spent about a year trying to find out what that disc is.
Martin Gant - had no idea
Brian Johnson - could not recall
Phil Tippet - had no idea
Harald Lystad - no idea
Thoose lads was the best hope. They had major roles in the production of ESB at Finse.
I guess some random boffin under one of those guys group built it.
I give up - im calling the V8 oil pump screen housing the correct part.
With that information - can we as a communtiy agree that the mystery knob is 95% the V8 oil pump screen housing part?
I mean, the odds that some other clue showing up is 3, 720 to 1