Certificates
A certificate of authenticity is not about trust, it is about the system. Even a buyer who trusts you completely needs the document — for the insurer, for inheritance, for resale. Without one a gallery will not take the work on consignment and an auction house will not accept it.
The registry keeps track of what you have issued: which work each
certificate belongs to, who received it, and which ones are still valid
rather than revoked.