Numista has this old FAQ
that is replaced by this more updated (part of catalogue guidelines)
https://en.numista.com/help/add-or-modify-a-mint-in-the-catalogue-189.html
https://en.numista.com/help/i-noticed-a-mint-is-missing-from-the-numista-database-can-it-be-added-28.html can be removed.