What is a PSA 10 Gem Mint card?

A PSA 10 is a card that Professional Sports Authenticator (PSA) has graded Gem Mint 10, the highest grade on its 1-10 scale. PSA describes a Gem Mint 10 as "a virtually perfect card": four perfectly sharp corners, sharp focus, full original gloss, no staining of any kind, and centering within about 55/45 on the front and 75/25 on the back.

PSA's standards write the grade as GEM-MT 10. There's no PSA 9.5, so the grade just below a PSA 10 is a PSA 9 (MINT).

Before you buy one

• Read the label, not the title. Read the grade off the label in the photos, and make sure the card in the slab is the card in the title: same set, same number, same edition.

• Look up the cert number on PSA's website, which shows the card and grade that number was issued for. If the photos hide the label, ask for a clear shot of the front of the slab.

• Skip the grade bait. "PSA 10 ready", "potential PSA 10" and "PSA 10 candidate" all describe a card nobody has graded.

• Pool the spellings when you compare. "PSA 10", "PSA10", "PSA GEM MT 10" and "PSA Gem Mint 10" are one grade, not four. When you line up copies, count every one of them.

A ChaseBoard PSA 10 watch reads "PSA 10", "PSA10", "PSA 10 Gem Mint" and "PSA GEM MT 10" as the same grade, and skips titles that call themselves raw or lean on words like "potential" and "candidate".