For something only four numbers long postcodes had an enormous impact on Australian society. When postcodes were introduced in 1967, there were sweeping technological advances that also came into place. Automation and the mechanization of skilled work meant that discussions around worker's rights and equal pay became louder. Industrial action and the right to strike played out on a hugely visible scale. Sending a letter to a loved one became an exercise in navigating a system that made people into part of an enormous machine.