No, your code is 7249, remember?
I doubt that's what it is -- my guess would be that's for a key or something. According to my manual, there are supposed to be a couple wallet-sized cards with the number on them.
Those cards didn't come with my car, which I found out after my first battery disconnection.
I tracked down the original dealer who sold the car new, and called them up. They were able to look it up from the VIN number. It helps to sound honest.
So remember kids, when you steal an MB radio, be sure to write down the VIN number!