When Saigon fell in 1975, the name of the currency was changed to “liberation dong” and each new dong was worth 500 of the older southern dong. Upon the unification of the country, the currency was unified as well. The dong was revalued in 1985, with each new dong equal to 10 of the old dongs. The dong has been rated as one of the least valued currencies in the world.
Each dong was originally divided into 10 “hao,” which are then divided further into 10 “xu.” The hao and xu have so little value at this time that they are no longer issued.