Anyhow, whatever the certificate may state, the year the person was born is 1949.
So perhaps the birth certificate states a different year, by mistake, or doesn't state the year at all, or perhaps states the year 1949 but is not really credible and can't be relied on. Be that as it may, we state herewith that the real year of birth is 1949.
"al margen de" does not normally mean "written in the margin of" but "not taking into account". "Written in the margin" would be "en el margen", not "al margen". I don't know too much about the formal jurisprudence language employed in certificates, but should a year on a birth certificate really be written in the margin of the paper instead of right in the middle of it where it belongs to?
It looks like they did in fact forget to add his year on the left hand side where only the day and month show. That is why below they added a few years ago this rectification statement. They do write it out on the right hand side but I guess they figured they needed to mention it on the left side as well.