He sold milkshake machines to the McDonald Bros.' burger joint, got curious about their operation & soon made history
The History Channel Magazine, 2005 ... Mac, made 
food with an assembly line in 1952 at their hamburger joint in San ... Ray Kroc, a 
curious and canny veteran of the food business, read the article ... Kroc, 50, was 
a top salesman of the Multi-Mixer, a machine that made five milkshakes at once.