Serial number for Dell accessories?

Hey all -

I've got a Dell Dock WD15 here and, for the life of me, I cannot find a service tag or serial number anywhere on it - and I'd really like to, given that we inventory and track all of our good stuff. I DO see a "CN" number out there that's rather long (and distinct from the "DP/N" which I'm assuming is simply the part number) is that the serial number?