Comm Slot 1 card is also a possibility for networking.

On reflection, and on being reminded that the Color Classic has the Snow White line and represents early Espresso design language, the fact that an Espresso design should have the line is not so surprising....

Still, a bit of googling turns up at least one image of a CD-less LC550 that does not appear to have the line, though the resolution on that one is not so good as to make me certain of it.