This is really a 1972 Rastrojero P68 made by I.M.E in Argentina. P68 means it had a steel pickup box.
The puzzle model was also known by the non proper model designation Caburé, but not Charrúa.
What the picture caption means is that the truck is in Uruguay.
Quote Wikipedia:"The Charrúa are an indigenous people of South America in present day Uruguay"......"Uruguayans refer to themselves as "charrúas" when in the context of a competition............"
In Argentina we use charrúa when referring to people or things from Uruguay.
Bellow is a picture of the same puzzle truck in 2012, owned by the sons of the original owner and supposed to remain in the family forever. The original owner asked to be carried to the cemetery in his Rastrojero.