OK...you got me. Case holder it is. My terminology is still a little weak.My vote is for a watch case holder (I have one quite similar, but made with more modern materials. The knurled knob adjusts the clamp for cases of differing sizes, and the padded posts keep the case firmly stationary. It is a priceless tool for when you have to unscrew the back of the watch case and replace it later.
And while you could in theory use it to hold a movement, I think the metal surfaces would scratch up the face of the inverted movement!
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BTW: as you're looking at the tool, the "lower" metal block needs to be rotated 180 degrees
so that both of the longer sides face each other!
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