This is a 16th century German so-called 'oath skull' on which defendants swore their oath in Vehmic courts. It is engraved with the Roman 'Sator square', a five-line palindrome, rendered in Latin, of five words: SATOR, AREPO, TENET, OPERA, and ROTAS.

This is a 16th century German so-called 'oath skull' on which defendants swore their oath in Vehmic courts. It is engraved with the Roman 'Sator square', a five-line palindrome, rendered in Latin, of five words: SATOR, AREPO, TENET, OPERA, and ROTAS.

Many scholars question the origin and meaning of the Sator square. This was first thought to be of Christian origin because initial examples of the grid dated to around the 3rd to 5th centuries AD. The square also held what were believed to have been hidden Christian symbols.

However, the discovery of what is now the earliest known inscription of the Sator square, on walls in the ruins of Pompeii, dates it to as far back as 79AD.