DriverZone.com: The place to find device driver updates.

Introduction:
Equipment that attaches to the public telephone network, called section 68 equipment, is assigned a different number by the FCC than most other computer equipment
By using Driverzone.com's online registration database and the FCC registration number, you can quickly look up the original manufacturer of the equipment.

The difference between the FCC Registration number and the FCC ID:
There are two different FCC numbers used for identifying computer equipment, the FCC Registration number and the FCC ID number. The FCC Registration number is used for "Connection of Terminal Equipment to the Telephone Network" or section 68 equipment. For a guide on how the FCC ID can be used, reference this guide.

Finding the FCC Registration Number:
In most cases if the equipment is in a case it is on a small sticker, in the back of course.
Or if it is an add-in card it is usually etched directly onto the PCB as is the case with this modem:

Searching using the FCC Registration Number:
The first three or four digits of the FCC registration number will uniquely identify who the manufacturer is. I find that using only the first three digits returns a more results, but may not list the specific modem I am looking at. So in the previous picture with a FCC Registration number of 4X2USA-25314-M5-E, 4X2 is what we want to search on.

So if we head on over to the search and enter 4X2 into the search box, we find that, that modem was made by 3com. Actually multiple records are returned for this search, but they are all different divisions of 3com.