At the Vietnam Memorial Wall, M.I.A. soldiers are marked with a cross by their names, and if they are found, a circle is circumscribed around the cross. To this day, the memorial has no circles.
The Vietnam War (or Vietnam Conflict, as it’s called now) was a pretty nasty issue that divided the United States in half. Though it’s now been over for decades, it’s still very often reflected on as a grisly piece of American history. The Memorial Wall dedicated to those who died in Vietnam sits in Washington DC. The names of all who died are etched into it.
The memorial is made of a very reflective kind of stone, so that when someone looks at it, his or her reflection can be seen too. The point of this is to “symbolically bring the past and present together.” In total, there are 58,264 men and 8 women whose names are inscribed on the wall. In addition to the names of those Killed in Action, there are names of those Missing in Action. About 1,200 are MIA, which is denoted with a cross. The confirmed dead are marked with a diamond.
If someone MIA is found alive, a circle is drawn around the cross, but this has never happened. If a death of a person previously thought MIA is proven, a diamond is superimposed over the cross. (Source)