one who seals or stamps a letter, a piece of writing, or a document (see Molina)
Alonso de Molina:
amatlacuilolmachiotiani. sellador de carta, o de escriptura. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 4v. col. 2. Thanks to Joe Campbell for providing the transcription.