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Thirty Too

Language Log traces thirty to the telegraph:

Back in 1859, Western Union established some standard numeric codes to be used for common telegraphic conventions (you can see the entire list here.) Telegraphy operators then and now have always sought ways to keep transmissions as brief as possible, since telegraphy is a relatively slow and highly manual mode of operation. A few of these codes are still in use today (“73” being the most common, used among Amateur Radio operators to say “best regards”).

According to the Western Union chart, the number 30 stands for “No more - the end.”

If the relevance of thirty is still unclear, it’s part of standard manuscript format, usually as #####. Thirty appears in sffms as the command to change ##### to a string of your choice, e.g., \thirty{–30–}.