Coins have been used as a form of currency across the world for almost three thousand years. Much like today, the earliest coins were formed from metals, with more precious metals reflecting higher monetary value. The most common shape of coin is a flat, rounded disc shape, which also tends to be small in size. Since the earliest coins, coin production - i.e. minting - has been a sophisticated process, with the Ancient Greeks and Romans demonstrating outstanding skill and technology in manufacturing. Whilst antique coins are valuable and coveted for their age, there are also rare coins from more recent years which can hold high value on the collectors' market; these include commemorative or special edition coins released to mark a specific event, such as military achievements, royal marriages and national anniversaries.