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(http://static.howstuffworks.com/gif/productImages/8/0/00000115180-KeyTronicLifetimeTrackballKeyboardmodelLTTBALLPS2-large.jpeg)
That's my favorite layout of all the keyboards I use. I own a black one and an ivory one. I wore out the black one (some keys, such as space bar, now have to be POUNDED to register) so I went looking and found a white one missing the ball for $5 USD.
Those clamp on trackballs were a pain in the ass to carry and set up, but the transition from a DOS laptop to a Windows laptop required it for me. Ah, CGA graphics. It all comes back to me.