Brian Wiser who is managing editor at Call-A.P.P.L.E. has found some information regarding the Essential Data Duplicator (EDD) card which before now wasn’t widely know. Major thank you to him and his excellent work on scanning it and making it available for everyone to see.
Here is the link: http://www.callapple.org/vintage-apple-computers/apple-ii/essential-data-duplicator-4-9l/