I am reading a book about Spanish California, and the author uses the word "rubric" to mean, I think, "personal mark attesting to a document." I don't have access to the original manuscript documents, so I can't tell if this refers to a signature, an "X," or some other sort of mark. Any thoughts on this usage?
Example from the end of a report (translated by the author from Spanish to English):
This is what we have seen.
Frontier of Santo Domingo, January 15, 1780.
Joseph Velásquez (Rubric)