Anvil face and headphones: what they have in common

1. Step 1. Anvil face — is part of — Anvil. A hardened working surface.
2. Step 2. Anvil — is made of — Bronze. Then bronze ones.
3. Step 3. Bronze — is material for — South-pointing spoon (Chinese compass). The spoon of the south-pointer rests on a bronze plate.
4. Step 4. South-pointing spoon (Chinese compass) — evolved into — Compass. A magnetic pointer.
5. Step 5. Compass — has part — Permanent magnet. The needle is a magnet.
6. Step 6. Permanent magnet — is part of — Headphones. A magnet moves the diaphragm.

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