I do not know if anyone noticed, but Steve Barber has supplied us with an excellent copy of Bak Seok-chang's (朴錫昌) 1711 survey map of Ulleungdo (鬱陵島圖形), which clearly shows Usando (所謂 于山島) as a neighboring island. Moreover, the map also describes Usando as having "fields of haejang bamboo" (海長竹田), which eliminates any possibility that Usando was Liancourt Rocks (Dokdo/Takeshima) since Liancourt Rocks were just barren rocks without the soil needed to grow bamboo. In fact, Korea's Dokdo Museum Director has admitted that the Usando on this map and others were Ulleungdo's neighboring island of Jukdo (竹島), which is about 2.2 kilometers off Ulleungdo's east shore. (See HERE) The map also shows in the middle of the island the three prominent peaks of Ulleungdo, which earned it the nickname, "Sambongdo" (三峯島 - "Island of Three Peaks").
Anyway, thank you, Steve, and I hope others express their appreciation, as well.
(Double click on the map to see an extra large version.)