How the round shape emergedThe shape of the first coins was determined by practical reasons and by the manufacturing process. Around the 6th century BC, in Lydia, in modern-day Anatolia, coins started to be produced by stamping ingots of precious metal with engraved dies by hitting them with a hammer. This process typically forces the metal into a rounded shape. Initially, the resulting coins were irregular, but as the technology was perfected, they became flatter and closer to a perfect circular shape. Most hammered coins continued to be round, for practicality: round dies do not need to have aligned axes, compared to square dies for example.
First square coinsAround the 5th century BC, early coins of India were produced by pressing several small punches into large metal sheets that were then cut into small pieces. Cutting square or rectangular pieces was easiest and resulted in the least amount of waste leftover metal that needed to be remelted.
Early cast coin shapesCasting was another popular coining process in Antiquity, in areas like China and Thrace. Casting was regularly used for the fabrication of tools and weapons. Primitive coins imitated the shapes of other commodities, such as arrowheads, knives, and spades (weeding tools). The coin casting process continued to be refined and around the 4th century BC, the first coins with a hole were cast in Ancient China. The hole allowed several coins to be stacked on a square rod so that the rough edges could be filed smooth. The hole was also convenient for carrying coins on a string for ease of handling.
Modern coin shapesShapes of contemporary coins continue to be partly driven by tradition, but also by practicality. Round coins continue to be the most popular, due to the fact that they can roll, being suitable for automatic machines. Reuleaux shapes have constant diametre, being also suitable for automatic machines. Other coins have intricate shapes to deter counterfeiting, or to be easily distinguishable by people with visual impairments.
Symbolic shapesContemporary novelty coins often have symbolic or realistic shapes, such as outlines of cars, animals, guitars, maps, globes, etc. However, this is not a contemporary invention. In Antiquity, Olbia used primitive currency shaped like a dolphin. Later, in the middle ages, in the Khmer Empire, coins shaped like a lotus flower were the first scalloped coins with a wavy outline.
The table below lists a range of basic shapes used in Numista to describe the shape of coins and exonumia. Novelties and more specialised shapes are not included in this list.