Historical Reserve Currencies:

1. Portuguese Escudo (1450-1530): ~80 years

2. Spanish Real (1530-1640): ~110 years

3. Dutch Guilder (1640-1720): ~80 years

4. French Livre (1720-1815): ~95 years

5. British Pound (1815-1920): ~105 years

6. U.S. Dollar (1920-present): ~104 years so far