Thank-you, @Quoth, for the notes and especially the photos. My wife would have shot me if I'd opened mine.
The photo of the battery clears up one point: the specification at
https://ebookreader.dk/shop/y-ben-p4...ser-1121p.html indicates two different capacities: 350 mAh and 1500 mAh. The battery itself shows 800 mAh, which is the capacity stated by
https://goodereader.com/blog/product...h-e-ink-screen.