The arms are those of Meras la Plaza with Solis in base for Pedro de Meras (born c.1630) who married Dona Catalina de Solis. Although the fourth grandson, he was named after his grandfather and became head of the house of Meras. His great-grandfather, Sancho Garcia de Meras, married Aldonza Martinez de la Plaza, sister and heiress of the celebrated Asturian captain Garci Fernandez de la Plaza.
The enamelled arms are charged with symbols which commemorate Garci Fernandez de la Plaza's valour in the 1535 campaign led by the Emperor Charles V against the brothers Barberossa who had captured Tunis. He distinguished himself in the capture of Oran, took part in the brutal sack of Tunis, and finally cornered the elder Barberossa brother, Arudj, with four of his captains, all of whom he beheaded. He was subsequently granted the right by Queen Joanna the Mad and her son, the Emperor Charles V, to wear on his coat-of-arms representations of the five heads, pennant and scimitar.
The Meras family seat was in the parish of San Pedro de Paredes in the commune of Valdez in Asturias. It seems likely that the casket would have been made locally and, if that was indeed the case, then in all probability it was made in Leon, the major goldsmithing centre of Asturias.