Let me start by distinguishing between two types of fake coins. One type are metals that are described and sold as coins, for example, football games start with a coin flip. Sometimes these so-called coins are produced for the express purpose of that coin flip and replicas are sold as coins. Well, they're not coins at all. This is just an illustration of the point I want to make. There are many other examples. Metals are around discs of metal. Coins are legal tender issued by a sovereign nation. Football is big, but so far the owners don't exercise any sovereign powers.
Well, they're counterfeit coins, and they're a much more serious problem for buyers. And just about any coin that is sold today is being counterfeited. Ancients, precious metal coins, and rarities. Advances in production technology, global trade, and internet sales have made it much easier than ever to produce, market, sell and deliver counterfeit coins. To protect yourself, buy legal tender coins issued and backed by a government with the authority to identify, prosecute, and imprison counterfeiters. Counterfeiters take that risk very seriously.
Buy from reputable dealers, not from people or companies you come across on the internet. Know your source. Be especially careful about Chinese sources. And finally, stop and think. Is this offer too good to be true? When it comes to precious metal coins, if it's too good to be true, it is, in fact, too good to be true.