I could find very little regarding the dark emerald green case and wanted to share pictures for anyone who is curious. it's definitely the darkest, I would even say forest green. it's a shame they didn't make a matching Kindle for it.
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I semi recently received a gift from a friend that is essentially a time capsule. He worked at a scrap yard back in 2012 and spotted this White Kindle Keyboard (K3G) sitting on a pile to be scrapped. He grabbed it, saw the shattered screen, and tossed it in a box where it sat for 14 years... he gave it to me and I got a new screen and battery installed and it's working like new. after checking the original files and the serial numbers on the board I was able to figure out that this was produced sometime around 2011 and only had 3 months of operation time before the screen was shattered.
as far as jailbreaking goes it was absolutely worth it. there's an excellent YouTube video that I followed. I have legacy ko reader running with simple UI. you can't do a lot with simple UI, but the bottom bar and the folder covers definitely makes everything nicer. unfortunately you can't use the text to speech feature in ko reader, but you can boot up a song in the stock OS then boot over into KO reader and have it play in the background. only the one song will play and you can't adjust the volume stop or pause it. so I just put a couple of 1 hour ambient songs on it.
the only thing stopping this Kindle from being perfect is the lack of a front light.