Installing a system from scratch can be a bear when it comes to finding device drivers, especially when the device in question doesn't have a manufacturer, model or even name associated with it. The latest install in which I had to deal with this was a Dell Latitude D430, but this device seems common to other D-Series Latitudes like the D620.
It's listed in the Device Manager simply as Data Interface with the typical unknown icon, and there were two of them. Digging further into the details of the device yielded the Hardware ID values below.
Turns out these are for the Verizon cellular modem card and drivers are readily available from Dell, under Technical Support, with your trusty Service Tag. I found the Verizon WWAN Card driver under the Communications heading (as VZW Mobile Broadband).