Wavy edges, keyed heels, and why most field horseshoes are younger than they look.
Iron horseshoes are frequent farmland finds and chronically over-dated. Genuinely medieval shoes tend to be light with a wavy outer edge and countersunk rectangular nail holes; post-medieval and modern shoes grow heavier, smoother-edged, and often add calkins (turned-down heels) or toe clips (a modern feature).
An ox shoe is a giveaway shape: oxen have cloven hooves, so they were shod with pairs of half-moon plates — a single curved plate covering half a hoof. Pony, donkey, and horse sizes overlap, so width measurements matter.
Rust obscures detail, so photograph after gentle dry brushing only. Record length, width, nail hole count and shape, and any clips or calkins. Be honest: without a stratified context, most shoes date no closer than 'probably 18th–20th century' — the wavy-edged exceptions are the prize.
Identifying harness and horse fittings