An independent company examines an item, decides its condition, gives it a number, and seals it in a case with that number on the label.
Common for trading cards, comics and coins. The sealed case is often called a slab.
What it actually buys
A condition opinion that is not the seller's. The whole point: the person judging has no stake in the sale.
Usually authentication too. Most graders will not grade a fake, so a graded item has cleared that bar as well — which is often worth more than the number.
A sealed state. Nobody has handled it since it was graded, so the condition cannot have changed.
What it does not buy
Not a Metzee verification. Metzee has no grading of its own and does not check or convert anybody's grade. There is no field for it, no badge for it. A graded item on Metzee is an item whose seller is showing you somebody else's label. How sellers are checked before they can sell
Not agreement. Two graders can land a point apart on the same card, and the same grader can on a different day. A grade is a careful opinion, not a measurement.
Not value. The number moves the price enormously in some categories and barely at all in others.
Not safety from fakes of the slab itself. Counterfeit cases with real-looking labels exist. Which is why the next section matters.
What to check in a show
The label, read out and legible. Serial number, grade, what the item is.
The case itself, turned over, under light. Graders build in security features and a seller can show them.
That the serial can be looked up. Every major grader has a public database. A seller confident in the slab will happily hold it still while you check.
A seller who will not show you the label clearly is the whole answer. Metzee’s position on counterfeits
Whether it is worth getting your own things graded
Sometimes. Grading costs money and takes weeks, and the sum only works on items where the grade moves the price by more than the fee.
So: for a common card, no. For something near the top of its ladder in a category where graded prices are much higher, often yes. The honest test is whether graded copies of that exact thing actually sell for more, not whether grading generally helps.
For sellers with ungraded stock
You are not at a disadvantage — most of what sells on Metzee is ungraded. Your substitute for a slab is live video and a straight answer: show the corners, tilt it to the light, say the worst thing about it. What do NM, VG and the rest mean?
More: what does deadstock mean, condition words, what is provenance.