# Certificate number

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**Certificate number:** The serial number a grading company prints on the slab of a graded card or comic.

## How we measure it

We copy it exactly as the listing shows it and leave it blank when the listing does not show one.

## What it is not

We never infer it from a link, and it does not prove the slab was checked with the grading company.

## Where it appears in the data

Field names as the API returns them; each dataset's page in the API lists the field's type and unit.

- `grade_cert` in dataset `cards_auctions`
- `cert_number` in dataset `comicconnect_results`

## Related

- [Trading card sale prices: how we collect them](/methodology/trading-cards/)
- [All glossary terms](/glossary/)