1WO means...

[Sailor Steve]

Midshipmen started out in the Royal Sailing Navy as novice officers. There was no Acadamy, and no OCS. A boy would go to see as a Midshipman and remain so until his superiors determined that he was qualified to become a junior Lieutenant.

As far as I know "Midshipman" is a title reserved for members of the Naval Acadamy or OCS.

Originally Posted by frau kaleun

I'm pretty sure though that Steve mentioned there being Warrant Officers during his time in the service? Which doesn't mean they're still there, but I guess I meant "modern" navy in a broader sense than just the years since then.

I don't know about today's navy either. Warrant Officer was technically between a Chief Petty Officer and an Ensign, but garnered all the respect of a senior officer, which a Chief already gets anyway, so I never saw what the point was (except maybe more pay).

Likewise 'Commodore'. In the US Navy 'Commodore' was a temporary title bestowed upon a Captain while he was in command of a squadron. In 1982 the official rank of Commodore was established, but in 1983 it was changed back to its original 'Rear Admiral (Lower Half)'.