Those are metal sewing thimbles.
They’re worn on the tip of your finger (usually the middle finger) to protect it while pushing a needle through fabric, especially thick material like denim or quilts.
You can tell by:
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The dimpled texture on the outside (that grips the needle)
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The closed top
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The small, cup-like shape sized for a fingertip
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Different metals (steel, brass, silver) and decorative designs — older generations often collected them
It’s very common to find a bunch like this in a grandma’s sewing kit 😊
Some of the fancier ones in your photo may even be collectible, especially if they’re sterling silver or antique.