When removable pull tops came to be recognized as a significant litter problem and safety hazard, can manufacturers searched for alternatives. The Coors firm, which had pioneered the aluminum beer can, came up with an “environmental package.” Six cans were sold held together with drops of glue, thus eliminating the need for any other wrapping, and the cans were opened by first depressing a small button to break the pressure seal and then punching in a larger button to provide a drinking hold. This awkward design soon led to today’s familiar can top.
From: The Evolution of Useful Things
By: Henry Petroski