> Great detective work

"Haussystem Didot" in the article's referenced typesetting catalog refers to the typesetting of the Didot family's printing agency. And they used that symbol 1700 and onwards in their map navigation descriptions in these books:

https://fr.wikipedia.org/wiki/Histoire_g%C3%A9n%C3%A9rale_de...

I am gonna repeat myself, but search for the Gallica links in each of those books to find the scans. There you can see earlier usage and evidence that as I pointed out in other - downvoted comments - that this was commonly used for sextant navigation instructions.