"Real gold" doesn't have to be 100 per cent pure gold. Most gold contains a small mixture of other metals to enhance its durability. Gold items bear a hallmark to show they have reached a legal standard for purity, and finding one of these marks is the best proof you have that the gold is real. Even if an item is unmarked, it's still possible to identify real gold by applying a number of tests.
Look for a hallmark. This will be expressed either as a three-digit number that represents the parts of gold per thousand the item contains or as "carats"--sometime spelt "carats"--which is an expression of purity as parts per 24 carat gold. Recognising a gold hallmark is relatively simple as only a few standards are widely used: 9 ct (375,) 10 ct (417,) 14 ct (585) and 18 ct (750.) The word "carat" can be abbreviated to "ct," "kt" or "K." Hallmarks are either impressed/stamped or laser-etched; they're never scratched in by hand. If you can't find a hallmark, move onto the following steps. (See Resources for more help with gold hallmarks.)
Weigh the item in the palm of your hand, and then do the same with another metallic item of a similar size. Gold is a comparatively heavy metal; if your palm can detect a greater weight, this is a strong indicator of real gold, especially when combined with the next step.
Find an inconspicuous place and scrape the with the end of a pin. Gold is a soft metal. If the pin makes a mark with little difficulty, this is good news. If the pin simply jars against the item without really penetrating, the item is made of some sort of base metal. Steps 2 and 3 are both quick unscientific tests, but taken together, they are extremely helpful in identifying gold pieces and excluding those which definitely are not gold. For a more scientific test, go to Step 4.
Test the item with a gold testing kit. These kits are available online from jeweller's accessory stores, and they contain vials of acid at different strengths to identify a variety of standards of purity. If the metal reacts to the acid by turning black, it means the metal isn't gold. If it doesn't react at all, then you have proven that the item is gold and the strength of the acid solution will also give you its caratage.