The earlier Greek coins were struck by hand. A single die was employed in the process, so that an impression of device or of legend appeared only on one side. The other side bore an indent which is known as the punch-mark. This mark is commonly a square figure divided into four smaller squares by lines resembling somewhat a right cross. It is the indent of the spike in the anvil on which the ball of metal was laid when being struck. Later, the coins were made thinner, and were struck with double dies. From that time both sides of the coin received an impression. The upper side continued to show the greatest care. As this side always bore the head of the god under whose auspices the coin was to be issued, it was called the obverse or face of the piece. The opposite side was the reverse. So long as coins continued to be struck by hand, there was no fixed relative position for the two impressions. Coins were always printed as though they were turned horizontally from left to right. They still continue to be so printed, and we go on in the practice of speaking of the reverse of coins, even when we are discussing those of our own coinage; but the fact is that ever since American coins were stamped in the mint the impressions on the two sides bear a certain fixed relation. In passing from the obverse of our coins to the examination of the opposite side, we do this by inverting the piece. That side would then properly be called the inverse of the coin, and it would, with equal propriety be printed directly beneath its obverse.