Thank you all again for your contributions.
Yeah, I managed the disassembling finally (without damage), after I startet to lift of the front display first. Due to that I stuck by the Buttons and the power connection to the display - as I finally got
, that there is also a backside available to lift off
(Nevertheless this was a good practice if I have to replace the display once - formerly I threw a PB IP3 away an buied a new one, due to sat an it = Display crashed.)
Found a very good WebSite, with also with videos and order possibilities:
https://e-ink-reader.ru/ (Don't be afraid from the .ru Domain - it is safe, you can even check the site by online tools)
Tomorrow I will post also my contribution with pics of the disassembling, some learnings and some questions about what I found inside the IP3.
Best regards.
Matthias