That's what I had suspected, I'd seen documents (online) from that time period referencing a Jose Monserrate Marxuach, but none referencing a Jose Maria. It could be that some archivist or government historian saw "Jose M. Marxuach" on some official document and simply assumed the "M" stood for "Maria," "Jose Maria" being a common enough name combination. A photo, if any exists, in the possession of the family could be compared with the official mayoral portrait for i.d. purposes (then again, brothers tend to look alike). This might be difficult to sort out. In any case, thanks again for checking. 

P.S. If this gets solved you might want to contact someone in an official capacity to let them know of the mistake (assuming there is a mistake), in which case you would be getting due credit for your thorough investigative work. Just a thought.72.221.92.43