It’s clear in retrospect looking at the initial photos of it in the salvage yard, taken moments after arrival that it was always missing one of the two trunnion knobs. I was worried that it worked itself free and fell off while I was pushing it home. Thankfully that was not the case. See here:

I went on eBay and I found the best replacement, which had less to do with finding the shiniest/newest one but instead one with the same exact markings.

It worked like a charm. It took some doing to get installed and I still need to pick up a washer but it’s a great start!

Now I have to polish up the other knob so they match.