I like the trackball better, too. Apple was inconsistent in where they silk screened the model number. 210s-270s usually had it on the bottom of the LCD panel, 280s & 2300s had it above the keyboard. The 2300 upgrade kit included a new 2300 series label for the bottom. Pictured here:

270c upgraded to 2300c, 2300c with top cover & trackball from 230, and 280c.

http://web.me.com/henryspragens/stuff/Photos.html#1