Signed & graded pieces.

Authentication and grading are two different services that arrive on the same piece of card, and confusing them is the most expensive mistake on this shelf. Authentication answers one question: is this ink what the seller says it is. Grading answers a different one: what condition is the object in. A piece can be authenticated and ungraded, graded and unsigned, or carry both — and the price of the third is not the sum of the first two.

There are only two ways a signature gets authenticated, and they are not close. In the first, somebody from the service stands at the table and watches the pen touch the item, then takes it away and seals it. That is a witnessed signing, and what it produces is not an opinion — it is a record of an event. In the second, the piece arrives in the post years later and an examiner compares it against exemplars: slant, pressure, the order the strokes were laid down. That is expert judgement, and expert judgement is a probability wearing a certificate.

Which is why a certificate of authenticity is worth exactly what its issuer is worth, and not a penny more. A COA written by the seller is a sentence the seller wrote about themselves. A COA from the promoter who ran the signing is worth something while the promoter still exists. A COA from a service that keeps a public registry is worth something because you can go and check it: type the number, and either the object comes back on screen with its own photographs or it does not. If the number does not resolve, the paper is decorative.

The slab is what happens when the claim is taken out of everyone's hands. The piece is sealed inside a tamper-evident holder with the service's label at the head, and from that moment the object is unhandleable and unphotographable and, in the market's eyes, is the number on the card. Cracking the case to look more closely destroys the grade, because the grade was never about the object alone — it was about the object inside an unbroken seal.