You may not know this, but Apple has been working on the iPad since before they started on the iPhone. Above is a photo of one of the iPad prototypes from somewhere between 2002 and 2004.
It looks pretty similar to an old MacBook. The photo of this tablet is codenamed “Prototype 035.” Apple’s Jonathan Ive pitched the iPad in court since he was deposed by Samsung to talk about the mock-up.
My recollection of first seeing it is very hazy, but it was, I’m guessing, sometime between 2002 and 2004, some but it was I remember seeing this and perhaps models similar to this when we were first exploring tablet designs that ultimately became the iPad.