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The marking, or hallmark, tells you what percentage of gold an item consists of. The hallmark is often printed on jewelry clasps or the inner bands of rings. It is usually visible on the surface of coins and bullion. The stamp is a number from 1 to 999 or 0K to 24K depending on what kind of grading system was used. Use a magnifying glass to help you identify the hallmark. It can be tough to make out by eye, especially on smaller pieces of gold such as rings. Older pieces of jewelry may not have visible hallmarks. Sometimes the hallmark wears off over time, while in other cases the jewelry never got a stamp. Hallmarking became common in the 1950s in some areas, but in India for instance, it only became mandatory in the year 2000. Most coins and jewelry are not pure gold, so they have other metals mixed in. There are 2 different scales used to indicate this through the hallmark. The number rating system used in Europe runs from 1 to 999 with 999 meaning pure gold. The U.S. uses a scale from 0 to 24K, where 24K is pure gold. The number rating system is easier to read than the karat rating system. For example, a rating of 375 means your item consists of 37.5% gold. What number means gold depends on the country you are in. In the U.S., for example, anything 9K and under is not considered to be gold, even though a 9K bracelet consists of 37.5% gold. Counterfeit pieces may have markings making them look authentic, so don't go solely on the hallmark unless you're certain you are holding gold. Some of the common letters you may see are GP, GF, and GEP. These letters indicate that your gold piece is plated, which means the maker put a thin layer of gold over another metal, such as copper or silver. Your item has some gold in it, but it isn't considered to be real gold. GP stands for gold plated, GF means gold filled, and GEP means gold electroplate. The markings vary a little depending on where the gold is from. For instance, gold from India contains a small triangle symbol indicating the government council responsible for the rating system. It then has a number rating and a letter code, such as K, for the jeweler. Gold is pretty soft for a metal, so plated gold often rubs away over time. The best places to check are around the edges of jewelry and coins. These spots often rub up against your skin and clothing throughout the day. If you see a different metal underneath the gold, you know your item is plated and not considered real gold. For example, a silver coloring might indicate silver or titanium. A red coloring could mean copper or brass. Pure gold doesn't react with sweat or oil from your skin, so if you see black or green marks, they are from other metals. Silver leaves behind black marks and copper leaves behind green marks. If you see a lot of these marks on your skin, your gold may be less pure than you expect. Keep in mind that most gold items are blends of gold and other metals. Even something like a 14K piece of jewelry, 58.3% gold, can leave these marks. Use other tests as well to ensure your gold is authentic.
Look for an official number marking on the gold. Use the number marking to determine how much gold is in your piece. Check for a letter marking indicating that the gold isn't pure. Find any noticeable discolorations where the gold has worn away. Note any discolorations on your skin from wearing or holding the gold.