We are all so comfortable with the Texas Instruments TI-99/4A micro, that we apparently keep forgetting its humbler and much rarer predecessor: the TI-99/4. Released in 1979 and sporting a calculator-esque keyboard while also lacking in graphics abilities, the computer was very soon surpassed by the 4A only to end up being the more collectible model.
To own one, do have a look at this pretty impressive Texas Instuments TI-99/4 auction. Not only will you be getting a working micro complete with everything you'll need to get it running, but also a great selection of manuals, guides, programs and games. Seller ships only within the US.