Spring in knob?

[Gfish]

Ah-ha! A slot! "By George, I think I've got it". Thanks buddy. When IQ fails me as it often does, I godda keep pushin it 'till I get it, or someone comes to the rescue.

[Midway Tommy]

Both of mine, 250 & Quick-O-Mat, have roll pins rather than a screw/bolt. I can't see with clarity deep enough past the brass threads to see if the insert is slotted but that is about the only scenario, other than possibly a slightly oversized hole, that makes sense. I do think, after close examination, that the threaded brass insert was slipped in, then the spring was added, a then the bottom of the drag know was crimped over to keep everything from falling out. I see no way to remove the insert or spring without uncrimping the bottom of the knob. I wondered if the oval top was jointed at the plate but I cleaned the grease off & it's not.