You have received a Legality certificate
Legality is a place where artists keep their work and the evidence that goes with it. When a file is uploaded, two things happen automatically: a fingerprint of that exact file is calculated, and a time stamp is obtained from an independent time-stamping service. The certificate is the page where those are published, together with the dates the author recorded.
How to check it without trusting us
This is the part worth doing, and it takes a few minutes. The certificate page offers the seal as a small file you can download. A time stamp of this kind is issued by an outside service under a public standard, and any ordinary cryptographic tool will verify it: the seal, the fingerprint it covers, and the moment it was issued. If the file the author holds is the same one you are looking at, the fingerprints match. If anything about the document had been altered afterwards, the check fails.
Legality plays no part in that verification, deliberately. Evidence that only works while a company is alive is not worth much, so the seal comes from somewhere else and can be checked long after any of us have stopped answering email.
What it usually means for you
Most messages of this kind are not the beginning of a lawsuit. They are somebody telling you that a design you are using, selling or licensing was made by them, and asking to settle it. The certificate exists so that the first argument, whether the work is really theirs and whether it existed before your use, can be settled quickly instead of being traded back and forth for weeks.
If the design reached you through a supplier, a marketplace or an agency, that is worth knowing: it happens often, and the practical question becomes where in the chain the file entered. If you believe the claim is mistaken, say so with your own dates. Either way, a reply is cheaper than silence: unanswered letters are the ones that turn into formal claims.
Who to talk to
Not us. Legality is not a party to the matter, does not represent either side, and does not give legal advice to anybody. Write to the author who contacted you; their address is on the certificate. If the amount involved is serious, take the certificate to your own lawyer, who will know what the dates mean in your country.
If you think a certificate on this platform is wrong or fraudulent, write to main@legality.art. We cannot decide a dispute, but a record that misrepresents what we observed is our problem and we will look at it.
A record page for one work: its dates, its fingerprint, its stamp. Nothing here is a mock-up.
Written plainly, and not legal advice. Rules differ by country and change; for a decision that matters, ask a lawyer in the country where the other side is.