- 30 -

De Wikipedia

–30– has been traditionally used by journalists to indicate the end of a story. There are many theories about how the usage came into being.[1] It was telegraphic shorthand to signify the end of a story in the Civil War era.[2] Other theories include that the "-30-" originated when stories were written in longhand; X marked the end of a sentence, XX the end of a paragraph, and XXX meant the end of a story. The Roman numerals XXX translate to 30.

The expression "No 30" at the end of a page (or a transmitted submission) signifies that the story isn't completed, and the recipient is to expect additional material. This helps to avoid inadvertent truncation.

Au Québec, Trente est le nom que porte la page Web de la Fédération des journalistes professionnels.