Figure of the month: 31.103 g
When comparing the current gold prices in Germany with those in the US, it becomes quite clear that the price differences cannot be explained solely by the currencies in which the respective gold bar or coin is denominated. It is, to a much higher degree, a matter of the different volume measures used: grams in Germany and troy (or "fine") ounces in the US, with one troy ounce equaling exactly 31.103 grams. These international differences in volume measurements have historical roots: the so-called metric system is common in most European and many other countries, whereas the British-derived system customary in the US reflects the British imperial system of measurements, "imported" to the new world by English immigrants. The main difference of the US and imperial system of measurements to the metric system is that there is no reference to the decimal system. The origin of the imperial system, by the way, does not go back to the former British Empire, but is a relic of the Roman occupation of England. The term "ounce" is derived from the Latin "Uncia", which in ancient Rome was the unit of measurement for a twelfth of a "libra", the Latin expression for "pound".
The terms "ounces" and "troy ounce" are frequently used unanimously with respect to gold bars or coins, which in many cases will not mean much of a difference. It is, however, wrong in the strict sense of the terms: the unit of measure "ounce" describes the gross weight of a piece of gold, whereas the "troy ounce" reflects the fine weight, i.e. the purity of a gold bar or a gold coin. The fine weight measures only the weight of the precious metal of a gold alloy, while the gross weight describes the total weight of said alloy. For example, the gold maple leaf coin has a purity of 999.9/1000: in this case, the gross weight equals the fine weight. With the South African Krugerrand coin, things look quite different: this coin has a fine weight of 916.6/1000. The gross weight of a Krugerrand coin thus is higher than its fine weight. The weight of gold bars is always listed in troy ounces or grams, respectively, since only the fine weight matters in respect of the price.