A copy is provided from the dept of health services/vital statistics adn they put the raised seal on the birth certificate. They would have a Notary put on a seal to state that it is a true and correct copy. All birth certificates are done this way.
We only had to show the certificates to the person who took our doc's at checkin (prior to boarding). They didnt even look at our drivers license! She just looked at the certificates and gave them back to us.
Keep them locked up in your safe. Take yoru sign and sail card and dr's license with you at all times!