Amstel is one of the more popular brands of beer in South Africa. I haven't made a clinical study of the facts, but I'd guess the four most popular (in alphabetical order) would have to be Amstel, Black Label, Castle and Windhoek.
Amstel beer was first produced in 1870 by the Amstel Brewery in Amsterdam, the Netherlands. According to a Wikipedia article, and to my surprise, it was taken over by Heineken International in 1968.
Although I find the beer a little bitter for my taste I do have many friends whose drink of choice it is. Perhaps my friends simply have a more sophisticated palate than I do...