That's actually what gave me the idea in the first place: I think the knobs resemble practice sprues [1] or jig holding points. The holes would likely have bee

That's actually what gave me the idea in the first place: I think the knobs resemble practice sprues [1] or jig holding points. The holes would likely have been cut using premade templates so the builders just used a different side pattern on each side, perhaps to demonstrate centering. [1] https://en.wikipedia.org/wiki/Sprue_(manufacturing)#Injection_molding https://en.wikipedia.org/wiki/Sprue_(manufacturing)#Injectio...