Happy to see the American educational brainwashing is still working strong lol.
What's so hard to believe that Columbus wasn't the first "outsider" to find North America? The Vikings did it 300 years before Columbus,and the Phoenicians certainly had the ships and knowledge to make it easily a thousand years or so before the vikings!
2 or 3 professor's,some institution in Boston,and a coin expert/author all agree these coins are ancient...but maybe they don't have the benefit of your expertise?
Anyhow,the last statement recommending contacting the author IS a very good plan,one i'd recommend doing.It could be you have a two thousand year old coin and a genuine piece of pre-american history.