That's not an MOS, that's an MOS number. Avoiding this kind of inexact meaning should be taught in school. Even widely experienced Marines don't know that many MOS numbers.
Oh nonsense, I still remember all 4 of my MOS. And it has been over 25 years.
My primary was 0311. Then I got my first secondary of 8151 at my first duty station where I was part of the Security Force. Then I got my secondary of 0411, Maintenance Management when I ended up doing that job at the Battalion level.
Then at my final duty station I got yet another secondary, of 8531, Marksmanship Instructor. While there I ran the Rifle Range, and that may even be a dead MOS number now as I think a decade or so back they moved that all to the 0900 training area.
But I can guarantee that there are a few MOS numbers that all Marines know. Specifically the 0100, 0300, and 0400 series. Because most love to put down the "stupid grunts". And every unit no matter how big has Admin and Supply. Now I could not tell the MOS between an Admin Clerk and a Postal Clerk, but I know they are in the 0100 section. And I do know what a MIMMS Clerk is, and while I do know that the warehouseman has a different MOS than the guy that orders replacement parts, all are in the 0400 series.
And almost every Marine should know 0200 is Intelligence, and 0600 is Commo. That literally follows the same numbering of the various S shops. S-1 is Admin, 0100. S-2 is Intelligence, 0200. S-3 is Operations, 0300 Infantry. S-4 is Supply and Logistics, 0400. S-6 is Communications, 0600.