Maybe there are two of them:
http://www.aliexpress.com/item/Kindl...535287073.html
http://www.aliexpress.com/item/Free-...744446423.html
But I would not call that finding definitive. (I could have made a mistake, they could have made a mistake, whatever ....)
What we really need is for someone who has both to tear them open and report the screen part number.
"Tear Open" because the K4 is the one glued together.
Note: As of the past week, the "Demo" K4 models on e-bay have been going for $30..$40 dollars, about the price of a new screen and Kubrick will un-demo a K4 in about 10 minutes.
(And you know the screen works, the ee-eprom is programmed, ...)