I often wonder why it is, for the sake of £20 worth of silver bullion, that the counterfeiters don't just do the job properly and be done with it? It depends when the counterfeit was made. A lot of the George III counterfeits were made then to spend as money, so the coin had to be made as cheaply as possible and look good enough to fool. Fakes made yesterday are made to fool collectors so although it would make sense to use silver, that would hit their profit margin - so they use something cheaper.