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I'm thinking circle cutter for making holes. I never thought much of them until I needed to make an odd size hole in a plastic panel (HDPE). With a sharp bit it cut a perfectly clean hole and the infinite size adjustment gave me a perfect fit. I'm not sure how it would work on hard materials but it's now my go-to tool for HDPE. This is a low rpm drill press or milling machine only item don't even think about using it in a handheld power drill. Make sure your material is well clamped down and keep your fingers out of the way!
The second one looks like someone made a set of clamps that fit in a T slot and hold sheet metal to table.
The first tool is exactly what everyone thinks. A hole cutter mainly for wood and plastic. I guess one could try it on metal.
That is a T-Slot Clamp. It is keyed into the slot and fastened to the T-nut im the slot. The screw hold the part etc. to the table. That would be a good clamp to hold a Machinist Vise in place. The bolt and T-nut are missing.