Head form and point.
Dress pins, hairpins, and sewing needles vary by head form and material — bone, copper alloy, or iron. Needles have an eye; pins a head. The head is the datable part: decorative bone pin heads change with fashion closely enough to date Roman examples by hairstyle alone.
Copper-alloy dress pins with wound-wire heads are the classic Tudor and Stuart find, lost by the thousand from clothing that was literally pinned together daily.
On needles, note whether the eye was punched or drilled and whether the shank is round or flattened — small details that separate periods and trades.
Wear at the point and polish from handling confirm use. Record length, material, and head form; a complete pin is a small object with a surprisingly precise date.
Identifying harness and horse fittings