Riveted rings and shaped steel from soldiers' second skins.
Mail survives as clumps or single rings. Genuine European mail alternates riveted rings (look for the tiny overlap flattened around a rivet) with solid or riveted rows; ring diameter is usually 6–12 mm. Butted mail — rings simply bent closed with no rivet — is almost always modern costume or reenactment work.
Plate fragments are shaped, not flat: subtle compound curves, rolled or turned edges, rivet holes and articulation slots along the borders, sometimes armourers' marks. Jack chains and splints (strips on fabric) also occur. Roman lorica fittings — hinges, hooks, tie loops — are a distinct copper-alloy family worth knowing.
For mail, photograph rings under magnification to show the rivets; for plate, record thickness, curvature, and every hole. Most 'armour' brought to experts is boiler plate or agricultural steel, so an honest description of edges and holes lets the board judge fairly.
Identifying arrow and spearheads
Identifying swords and daggers