Verify the certification number

Every legitimate slab carries a cert number that you can look up on the grader’s official site — the card, grade, and image should match. A cert that does not resolve, or details that do not match the slab in hand, is a red flag.

Inspect the case and label

Check the slab for tampering or reseals, fonts and hologram details that look off, and a label that does not match the grading company’s current style. Authentic slabs are hard to open cleanly; a case that looks reglued is a warning.

Buy from reputable sources

Stick to established sellers and major venues, and be wary of prices far below market. When you add a card to Slabline by its cert number, the lookup confirms the card behind the number — one more check that what you own is what it claims to be.