A five-drachma-in-the-slot sacred water dispenser designed by mathematician and engineer, Heron of Alexandria, is often cited as the world's first coin-operated machine, although Heron referenced a similar Egyptian temple device described in 215 BC. It was also Vending Machines which ushered in the coin machine age, towards the end of the 19th century. Designed to deliver a product, such as chocolate or stamps, in exchange for coins, there was supposed to be no element of chance. However, mechanical frailties often left honest customers short-changed, while the dishonest could get something for nothing. They only became truly reliable towards the end of the 20th century, with microchips monitoring their input and output. Their mundane function was sometimes offset by elaborate exteriors in a form of sculptural advertising.