The document you see is a certified statement that the facts attested to are as recorded in the specified book and page number.
Normally such a document is accepted at face value as a “Birth Certificate”. A similar doucment was accepted as proof of Birth in Indonesia when my wife applied for US Citizenship.
The “Original” is merely a consecutive page in a record book and will NEVER be removed. Normally authentication would consist of verifying that the record exists in the book and on the page specified. Unless, of course, a government thug goes to the archives and takes the page out at the point of a gun or at the back end of an envelope.
If that were to have happened, then there would be a gap in the sequentially numbered pages that would be so suspicious as almost to serve as authentication in and of itself in this case.
Thank you, John. Terrific, and very encouraging explanation.