Design Boom has just posted a gallery of photos showing off the work of Hartmut Esslinger, a German designer who worked with Apple in the early and mid-80s.
The gallery includes a number of gadgets which were never made, including the Macphone and a funky looking dual flat-screen work station, but it also includes a design from 1982 which clearly became the first Macintosh. There's also a photo from 1985 which hints at the design of the iMac, even though that computer wasn't released until a decade later.
Here's a couple more images (© designboom):
Update: DesignBoom has asked me to reduce the number of images in this gallery and direct you to their website to see the rest.
The one I like best is the MacTablet. There had been hints before that Apple had looked at that concept in the 1980s. That tablet, which was codenamed Bashful, was more of a fixed desktop touchscreen computer than what we would call a tablet today.
It's a pity that Apple never made the Bashful; it would have been expensive but it would also have turned computing upside down - again.