2 ms·
It's three exes (XXX) written as Arabic numerals (though they were never Roman numerals to begin with). "XXX" is an easily-identified marker; "30" is just cargo
by stan_rogers 9y ago
It's three exes (XXX) written as Arabic numerals (though they were never Roman numerals to begin with). "XXX" is an easily-identified marker; "30" is just cargo cult stuff.
- ghaff 9y agoThat's one of a variety of explanations but no one seems sure of the actual answer, e.g. [1] In any case, it was widely used for a long time. [1] http://archive.saila.com/journalism/thirty/ http://archive.saila.com/journalism/thirty/