You don't happen to have a Kindle DX Graphite somewhere near you so that you can make a comparison shot.
When you say the contrast is the same, this means, that the font has to be darker, right? Why are you so sure about the plastic substrate? I read
here and
here that the screens which were shown on fairs (e.g. Asus DR-900) had a glass backplane.
Greetz
Scheich Xodox