A Certificate of Authenticity — I'll call it a COA — is your assurance of the photograph's integrity. It's a clear record connecting a specific print to me, the artist, giving the work a documented identity. That matters when the image is part of a limited edition, changes hands, or ends up in a collection inventory.
Three things it establishes:
Provenance — where it came from.
Edition — the guaranteed limit on production.
Signature — my reputation on the line.
If you're looking at a piece and considering a real investment, you want that reassurance. The COA provides it — like a birth certificate, without the inked footprint. On it: my name, the date, the media, edition number and print run — all backed by my signature.