Are you sure it isn't DE-9?
I have never seen a nine pin connector in a DB sized shell. I have seen thousands of DE-9 connectors, and heard them mistakenly called DB-9 many times. But the only DB sized connectors I have seen in use were DB-25 or DB-13W3 units.
While technically true, I would say that is extremely pedantic. Everybody knows that the common 9 pin serial connectors are colloquially called "DB-9". At this point I think that about the only people who know what a DE-9 connector is are those who like to nitpick and show how smart they are, or people old enough to have worked with them in the late 60s-early 70s when D-shell connectors were new and cutting edge.
Same story with saying "RJ45" to mean 8P8C modular, I guess. The wrong name is so ingrained (and the actual Registered Jack standard is so old and disused) that it doesn't matter any more.
(Though I still get mildly annoyed when someone says "RJ45
cable"...
)
D-Sub is an interesting choice for USB though, since it doesn't have the staggered pin pattern to ensure ground makes contact before anything else, it would make hot-plugging somewhat hit-and-miss.
Good score though, OP! Let us know how it turns out!