[crb3]

And (guessing here) you'd be SOL if there were already 9999 Susies registered when you tried to sign up.

Me, I'm gonna treat it like a firstnick.lastnick format when it arrives at my account. I figure "crb3.cdp1802" is very unlikely to be taken before I get there, but, if I'm wrong, there're lots of other already-memorized device-numbers I can append.