An Appostille gives full faith and credit of documents from one jurisdiction, to be valid in an other. For example for an AFFIRMATION from a notary in PR to be valid in Canada, I would have to go to the State Department and get those documents APPOSTILLE so they may be accepted in the other jurisdiction. It seems to be some international commercial treaty.
Yes! The APPOSTILLE carries TWO signatures from state officials, an official SEAL, and on the top you may see the party with surety, the government or agency issuing the APOSTILLE.