I noticed this round connector as part of my AV display on a recent flight. It seems to be a DIN connector but I’m not sure that the arrangement of leads is common. It doesn’t seem to be a PS/2 connector. I have no idea why the aircraft designers thought this connector was a good use of weight on their airplane. Did anyone ever use this thing?
Books by Marilyn Wolf 
It looks like a Panasonic eXport jack for iPods.
https://aadvantagegeek.boardingarea.com/2013/03/20/americans-new-777-300er-connecting-your-ipad-ipod-or-laptop-to-the-entertainment-system/
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