Security features and certification are important issues to Gold since there is little or no protection from the courts or the law. Fiat will settle "all debts, public and private". However, the authenticity of coins can easily be tested with simple devices which can be purchased. Also, a pair of calipers and an accurate weigh scale compared with a list of weights of known coins can be used check coins if one is familiar with weights and measures.
Security features and certification operate differently with paper currency than with metal money. With metal money, it is a verification of material or substantial content. With paper money consisting princinply of decimal numbers, the security features, along with the printed matter and paper, serve the purpose of distinction. Distinction is an act by which the mind represents one object to itself as not being the same as a second object(id quod ob-jicitur cognoscenti). Paper money provides only distinction because there is no significant difference in the material or substantial content of the authentic or the counterfeit note or of any one note to another. So then, though the material distinction of the paper, a five dollar note is distinct from a hundred dollar note and from a counterfeit note but not from a different five dollar note. Two different five dollar notes are considered the same.
That's a much better idea than biting down on each coin to see if it's real gold!
Amazingly you always see Olympic gold medal winners chomping down on their medal, checking, hoping that they actually got some real gold for their efforts. Unfortunately most will wind up having to sell the medal to pay for the resulting dental work.