Outdated reverse DNS. That IP address used to be a unique IP assigned to the customer you identified (in another datacenter), but it’s now a router. For a variety of complicated, annoying reasons, the old reverse DNS entry for that IP was never cleaned out, so it remained when we reassigned the IP.
Since you mentioned it, I’ve gone ahead and flushed out old reverse DNS entries for that network, and a more accurate (but less interesting!) hostname for that router should show up soon.