I recently saw the exact same thing at the top of a notarized document. I wrote to the notary and he confirmed it was the initials of the clerk who draws up the documents for signature. If your document was issued by a notary office in Oviedo, Asturias, it is highly likely the same person drew it up.
Recommend this solution for most unexplained initials placed at the top of a notary document between the seal and the body of the text.