Every sealed letter is hashed on sealing day and the hash goes on the public registry. The letter itself stays private until its opening day. When it opens, you can check that not one word changed:
payload = TRINESCOPE|TS-XXXX|sealed YYYY-MM-DD|<canonical-JSON> hash = SHA-256(payload), uppercase hex, shown as 16 groups of 4
canonical-JSON means: UTF-8, Unicode NFC, object keys sorted, no extra whitespace. The opened record page shows the letter’s canonical JSON verbatim, so the payload can be rebuilt character for character.
Recompute the SHA-256 of that payload with any tool you trust. It must equal the hash that has been on the book since sealing day. If it ever doesn’t, we changed our words — and you caught us.
No birth data enters the payload’s public parts, the registry, or this page.