[X] Keep it a secret publicly, but pass some quiet words through your representatives in the Free City of New York that you have what you believe to be the Declaration, and would appreciate their confirmation. Massive opinion boost with the Free City of New York, +2 Legitimacy as they automatically recognize you.
[X] Make it known to the world that you possess the Declaration of Independence, and invite the Free City of New York to Chicago to examine and confirm the authenticity of the document, as well as discussion possible restoration efforts. +8 Legitimacy, massive opinion boost with FCNY, large opinion boost with most polities within the former borders of the United States, negative attention from Japan, Russia, and Russian client states.
[X] Keep it secret, keep it safe. You're already enough of a target, as a Revivalist state. You don't need more reason for Alexander to put a kill order on you.
[X] Secretly inform the New California Republic and the Free City of New York that you have what you believe to be the Declaration, and would appreciate their confirmation (as well as discussing possible restoration efforts) with a coordinated public reveal to occur on July 4th, 2076.
[X] Publicly gift the Declaration to the Free City of New York. Max out relations with the Free City of New York. -3 Legitimacy, as this is very not the move of somebody who believes themself to be the legitimate successor to the United States of America. Also suggests some things about what you think about the rightful state of your relationship with FCNY.