Follow the link to see concept work done by Hartmut Esslinger, designer of the Apple IIc. Among them, a design for a future (for 1984) phone in co-operation with AT&T.

http://fudder.de/artikel/2007/07/17/origin-of-the-iphone/artikel/

[Update] see also: Appledesign: The Work of the Apple Industrial Design Group
http://www.amazon.com/Appledesign-Apple-Industrial-Design-Group/dp/1888001259
(thanks +Charis Tsevis)
[Update] the book mentioned above is rare to find (Amazon sells it used for $500), but here is an excellent source on the issue with information and photos copied from the book http://liquidpubs.com/blog/2010/11/08/apple-their-tablet-computer-history/

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