I posted this over in the FB prop group, but I'll post it here so there's more eyes on it. When I look at this pic:
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...and now knowing it is a camera-related thing, I was wonder what might have that curved underside. It occurred to me that it might be a light rigging device.
Here's a modern one:
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Basically, when you do stage light rigging for movies, theaters, concerts, etc, most of the time above the stage there is a grid of aluminum pipes hung from cables. Idea beaing that you can clamp a light on anywhere on that grid and adjust as needed. If the piece we're seeing on the kobold above was the upper half to something meant to be tightened around a pipe and the top side was a light or camera mount, I think it could this sort of device from the 70s. It certainly would have been readily available on a soundstage.