Help identifying pieces that came from a vintage test equipment auction

Sorry to be so vague, but I have 10 or so of these in varying sizes and shapes and for the life of me have no idea what they are. There used to be labels on two of them, but they are too faded and damaged to read any pertinent information. I think they came out of/off of some of the vintage test equipment there... but there were also a lot of vintage car and motorcycle parts, as well as airplane parts.

The wheels/cogs/gears in the center turn. There are usually two sets and they both can turn independently. Some rotate 360 degrees and some only 180.



It was a metal working shop, so maybe they even got tossed into the test equipment auction by mistake. They are too cool to scrap. Any information would be greatly appreciated.

Thanks and Merry Christmas!!
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Variable capacitor - Wikipedia, the free encyclopedia

There is a market but you would have to know the value of the component.

Air Variable Capacitor | eBay