That kind of general knowledge does not hold any water. We all wish what we've collected is not only genuine, but rare. But do not do that by denying how inauthentic someone else's is, or just saying it is simply a conterfeit. None of us was born, brought up 300 hundred years ago. What we do is to presume. Did you eyewitness the process of forging such a coin 300 years ago? If your answer is negative, what you said is not more than a personal judgement.