What is a slab in card collecting?

A slab is the sealed, tamper-evident plastic holder a grading company puts a card in after grading, with a label that names the card, its grade and a unique certification number. PSA describes its holder as a sonically sealed, tamper-evident case, and CGC's case is ultrasonically welded. "Slabbed" is shorthand for graded.

The slab is what holds the grade, so it matters as much as the card inside: PSA treats a card removed from its holder, or found in a partly opened one, as never graded.

Before you buy one

• Look up the cert, then look at the case. First, look up the cert number on the grader's own site. Then compare the holder and label with a known-real slab from the same grader. PSA publishes tamper signs to look for, such as frosting or cracks along the edges of the case.

• Filter out the empty cases. Sellers write "slab", "slabbed", "graded slab", "PSA slab", "BGS slab" and "CGC slab", and a search for "PSA slab" also returns empty slabs, cases and stands. On eBay, put a minus sign in front of a word to exclude it, such as -empty.

• Pick the grader if you want eBay's check. eBay's Authenticity Guarantee accepts slabs from PSA, SGC, CGC (and CSG) and BGS. TAG isn't on eBay's list, so factor that in before you buy.

ChaseBoard can watch for a card graded by PSA, BGS (Beckett), CGC, SGC, TAG, ACE, ARS, AGS or GMA, and any watch can carry exclude words such as "empty", so the cases and stands stay out of your alerts.