There is a "Datong Archive" online and maybe someone in their community would be interested in buying the unit or preserving any manuals that you have. Their website: https://sites.google.com/site/datongarchive/
If the keyboard has a model number etc. you might want to include that in your sales offers.
Also see this where someone is specifically asking for a Datong Morse keyboard: http://uk.answers.yahoo.com/question/index?qid=20120805060600AA16wP2
I personally think that CW keyboards are kinda neat, but have never actually used one :-)