...some sort of naval set.
It's the same exact set (NAF Set No. 1108-1), just supplied by a different source than Plomb.
There's a classic GJ story behind this. On November 8, 2018, I found and posted a spinner and a sliding T on the 'Midget drive tools' thread, because they were abnormally fat and unmarked, linked
here. A few weeks later, quite by happenstance, Odes posted a Phila Mfg. Co set he had found, linked
here. Beemer immediately noted the resemblance to my fat spinner and sliding T, and within days it was confirmed that's what I had found. I identified the set as the same as the Plomb NAF sets from the NAF ASO Class 41 catalog I have. Then, in January 2019, you picked up your "oddball" set off eBay, linked
here, apparently forgetting my earlier spinner/sliding T and Odes' set confirming their provenance. And I've been trying to talk you out of it with things from my collection and the kitchen sink ever since!
I wonder if any other sources will show up. My bet is yes.
Here is an excerpt from the NAF ASO Class 41.