1WO means...

[HW3]

I'd think those ranks would more likely be seen at the Second Watch Officer position, with an Oberleutnant at 1WO, unless of course the kommandant was still an Oberleutnant. May have been much more common though as the war went on and training time was cut short and the number of available officers overall declined.

I agree frau that it was probably that way at the start of the war but, with Admiral Donitz rapidly building up the u-boat force as fast as he could from the start, I think that changed rather fast. I have noticed that a large number of kaleun listed at uboat.net were only Oberleutnant's when they first took command. I am also fairly sure that there were more than a few new Oberleutnant's as 1WO with a more experienced Oberleutnant as Kommandant. Of course this is just my opinion, and I could be way off base here.