In the late 9th century when Gualtiero I was the bishop of Luni, Adalberto II, the son of the founder of the abbey, wanted the relics of St. Caprasio to be brought from Provence to Aulla. The relics were kept in a wooden reliquary and were buried in a grave below the altar.
In the first decades of I lth century the abbey was enlarged. In order to host the body of the Saint, the monks put the relics in a stucco case which was laid inside the new monumental grave.

The corners, nails, locks and hinges of the wooden case which had got in contact with the bones of the Saint were regarded as precious “contact
relics” and were therefore kept in the former grave which was no longer in use.

The fragment of the marble architrave may be a part of a small architectural complex, maybe a ciborium (a canopy over the altar) which
was built over something important. It dates from the second half of Sth century and 9th century and was probably made to recall the presence and the burial of the Saint. Giovanni Mennella proposes the following interpretation:
(—extru)cta ob diem (?) (—)
which may be a reference to the building commemorated by the dedication on the architrave.