thumb|The weave of calico sample from a shopping bag shown against a centimetre scale Calico (; in British usage since 1505) is a heavyOxford Advanced Learner's Dictionary of Current English ISBN 019
1. Compute SHA-256 of OTSCanonicalRecord value → must equal OTSHash 2. Open OTSProofURL → extract Bitcoin block number → must equal OTSBitcoinBlock 3. GET OTSBitcoinBlockVerifyURL → returns the Bitcoin block hash at height OTSBitcoinBlock; GET https://blockstream.info/api/block/{that hash} → its timestamp must match OTSTimestamp 4. Read CopyrightID inside OTSCanonicalRecord → must equal the CopyrightID above 5. GET OTSVerificationAPI → pre-computed 6-check result from server 6. If all match: this entity was registered on CopyrightChains at OTSTimestamp, independently verifiable on Bitcoin Note: an OTS proof may carry multiple Bitcoin attestations; OTSBitcoinBlock is the earliest confirmed one — a later attestation inside the proof corroborates it and is not a mismatch
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x02c8b02cf3bbb2f6737067a1d021846b0188a5b2e1f89a0e05daa9bfbfbbcc57. Chain 2 (Bitcoin): anchored in block 954066 (2026-06-17T08:11:48Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/61237db7-dcdb-42f2-979e-e3e735735d3b.json and https://artists.proofprofile.net/proofs/artist/61237db7-dcdb-42f2-979e-e3e735735d3b.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).