If you are thinking of buying some gold Krugerrands, South Africa's official gold bullion coins, then it'd be a good idea to become familiar with this unique coin. Essentially, you really should develop the skills to determine if a Krugerrand is fake. Hopefully, you'll never need this skill, but it is good to have nonetheless and it's reliably easy to learn.
The easiest way to avoid purchasing a fake Krugerrand will be to deal only with a reputable vendor, particularly a coin seller who specializes in or has an extensive experience with Krugerrand coins. These dealers will have been dealing with these coins for some time, and they should easily be able to notice when a coin does not feel right. What's more, reputable coin vendors will be concerned about their reputations, so they'll definitely have an incentive to ensure that they only offer genuine gold coins.
While that is one step you can take, remember that it's also reliably easy to verify the authenticity of a Krugerrand on your own. Standards for these coins are published by the South African Mint and publicly available, so you can compare the coin you are thinking of buying with these standards. In addition, you should be aware that gold has some special characteristics that make it unique. Specifically, it has a very high density, higher than the other easily available metals. If someone does decide to create a fake Krugerrand fashioned out of one of these other, lesser metals, the weight differential should really be absolutely noticeable if you know what it is you should be looking for. And you should be aware that the metals that are as durable as gold are either very difficult to acquire, very steeply-priced, or pretty brittle. All of this is in your advantage when trying to spot a fake.
In terms of physical characteristics, this is what you should be looking for: a 1 ounce Krugerrand has a weight of 33.930g, a diameter of 32.77mm, a thickness of 2.84m, and 160 serrations around the edge. A half-ounce Krugerrand has a weight of 16.965g, a diameter of 27.07mm, a thickness of 2.215mm, and 185 serrations. A quarter-ounce Krugerrand carries a weight of 8.482g, a diameter of 22.06mm, a thickness of 1.888mm, and 150 serrations. And finally, a 1/10 ounce Krugerrand carries a weight of 3.393g, a diameter of 16.55mm, a thickness of 1.35mm, and 115 serrations.
In order to carry out these tests, you will want a fine-grained ruler that has millimeter marks plus an accurate scale that can weigh in grams. As a substitution, there is also a very useful gadget known as the Fisch Tester that can test all of these things for you. It comes with a coin-shaped recessed used for checking shape, a slot for checking a coin's thickness and diameter, and a fulcrum to check a coin's weight. The Fisch Tester will save you time and effort and can make it much easier for you to spot a phony. At the same time, you should be careful about buying a Fisch Tester on eBay because, in a twist of irony, there have been some reports of imitation Fisch Testers being offered there. To be safe, you may want to buy directly from Fisch.
Armed with this new knowledge, you should now have the capability to detect a phony Krugerrand on your own. Best of luck in your adventures in the gold market!