It's just the Brotherhood Of Steel symbol from the Fallout game series. I pulled it off google, and then used an online converter to make it a .TGA file.
Placed it in the folder C:\Ubisoft\SilentHunterIII\data\Emblems\SubEmblems
This makes it available in game when you're choosing your sub emblem.
The file is here if you want it...
DropBox