Pay into escrow. The contract releases payment only if those serial numbers have never been retired, and refunds you if they have.
Buyer pays into escrow. Escrow pays the seller, or pays the buyer back.
Every sale appears here, one step at a time: payment locked, certificate read, ledger checked, outcome.
A retired serial range can never be retired again. Money stays locked until the check finishes. A rejected sale can be refunded, and nobody can edit or delete the ledger.
That the certificate is real. That check happens off-chain, by a trusted key. AI only reads the certificate, fixed rules validate it, and the contract decides who is paid.
Double counting across other registries. Solus checks the ranges it has seen, so going further needs registries to share their retirements.