The aforementioned underlining of keywords could also be done using overstriking.

Evidence of overstriking appears as early as about 500 BC when coins of Aegina were overstruck by the ancient city of Kydonia on Crete.

Thus, for example, the overstriking by cities in southern Italy of coins of Corinth has enabled a definite date of about 335BC to be established in the sequence of coinage produced at those south Italian mints.

When he enlarged the image greatly, the difference between the ink Jefferson used when he wrote the letter and the ink he used in striking out the offending material became clear, he said, and he used a computer program to remove the overstriking on the computer image almost dot by dot.