Since someone bumped this fairly recently, I figured I’d add to it.
The III was NOT the third model; it is the fourth (or fifth if you count the plus as a separate model, but since it’s still based off of the same motherboard that the original is, we’ll let it slide).
People always forget the Portable 286; this was a machine that came after the Plus, but before the II. It is a 286 AT class machine housed in the same case as the original and Plus. When it’s all buttoned up it looks identical aside from saying “Portable 286” on the outside. When you open the unit you are greeted with an AT keyboard, versus the standard XT layout of the original and Plus.
Just google “compaq portable 286” and you’ll see what I mean.
Compaq - “It simply works better”
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