First of all thank you for your thorough answers and how quickly you responded
It was a little bit of a bummer to hear they might have the language locked as I found many well taken care of 350 and 650 and other Sony ereaders on mercari Japan. (I have read your PM however so I will get in contact later today for that).
A question that did arise when looking at units was: 1) Whats the material for the buttons?