These are Acorn Nut Screws. They are also referred to as "Luke Rivets" for knife handles. This version is 0.250 inch diameter with brass heads.
Acorn Nut Fasteners - Luke Rivets for Handles - (.312 HD x 8-32 US x 1 L) - Brass
200 Pcs Nylon Acorn Nut, 7 Sizes M3 M4 M5 M6 M8 M10 M12 Black Dome Bolt Nut Hexagon Protection Cap Cover with Storage Box, Assortment Plastic Nut Kits for Bolts Screw
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Acorn Nut Fasteners for Knife Handle Attachment, Luke Rivets
Mardatt 100Pcs 7 Sizes Hex Acorn Cap Nuts Assortment Kit M3 M4 M5 M6 M8 M10 M12 Nylon Female Thread Bolt Cover Cap Dome Nuts for Protection, Indoor and Outdoor: : Industrial
Pommel - Floral Scroll Cap w/Loop - Bronze
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Mardatt 100Pcs 7 Sizes Hex Acorn Cap Nuts Assortment Kit M3 M4 M5 M6 M8 M10 M12 Nylon Female Thread Bolt Cover Cap Dome Nuts for Protection, Indoor and Outdoor: : Industrial
Sheath/Holster Making Foam - Thermoform Molding - (Maxx Form