Differences between these? Or are they really the same thing? How can one tell which model is which (if they're different)? I can find a number of auctions on them, but it's really hard to tell what's what. Some that don't SAY 3003C on the back actually are advertised as such. I have one, but I want another (one for work, one for home), and so do a couple of coworkers. Ahem . . . please no spiels about the differences between the 3003 and the 4004. I'm aware of the advantages of the multitudinous buttons, and I don't really care. TIA 'Sporky'