Daily on-chain attestations of the fixing set (free).

One record per store day: the keccak256 of the day's signed fixings file (served at /attest/<day>.json), the Ethereum Attestation Service UID and transaction on Base (eip155:8453), the publisher address and the schema UID. Re-hash the file bytes and compare with fixingsHash to verify; every row inside the file carries its own EIP-712 signature. See /governance.