I've seen dozens of "actas" from the civil registry during the time I've been translating here in Mexico, it's got nothing to do with levels or grades I'm afraid.

In Mexico State certainly, and I believe in several other states if not all (excluding the now defunct Federal District), the branch offices of the civil registry are called "oficialías", and the registrar in charge of them is called the "oficial". Each municipality may have one or more of these offices, which are numbered within that municipality. So, where it says "Oficial Tercero" it in fact means "Oficial de la Tercera Oficialía". Sometimes this registrar can be in charge of more than one "oficialía", so you might have "Oficial 02 y 05 del Registro Civil", which would translate as "Registrar of the 2nd and 5th Civil Registry Offices".

Here is a document showing you the personnel of these "oficialías" in Mexico State. As you will see the people shown in the rows marked in green are the "oficiales", who head up the offices and are responsible for signing the certificates. You will also notice the column marked "Of." contains numerals only, i.e., the number of the "oficialía" and the column of the "función" contains the title of the "oficial". In some places the title is written as "OFICIAL 02 Y 05 DEL REGISTRO CIVIL" for example, while in other it's written as "OFICIAL DEL REGISTRO CIVIL 01 Y 02". They don't seem to see much difference in writing it one way or the other, that's all.

http://dgregistro_civil.edomex.gob.mx/sites/dgregistro_civil...

I say all that for the benefit of the other respondents to this question, since I assume Andrea would be well aware of the system.