Different currencies were simply different weights of physical gold, and the exchange rate between one nation's currency and the other was the simple conversion between different weight units, as straightforward as converting inches to centimeters. The British pound was defined as 7.3 grams of gold, while the French franc was 0.29 grams of gold and the Deutschmark 0.36 grams, meaning the exchange rate between them was necessarily fixed at 26.28 French francs and 24.02 Deutschmark per pound.
