The casket has been dated anywhere from the early fourth to the early fifth century, but a date in the late fourth century is commonly preferred. It is 32 cm long, 22 cm wide, and 25 cm high. The casket may have originally been made in Mediolanum (modern Milan), in the north of Italy. The reason is that the two shield designs on the lid (the scene with the arrest of Christ) where the soldiers have contemporary fourth-century tunics, leggings, and shields, were identified with the Scholae Palatinae units stationed in Milan in the Notitia Dignitatum, a document which may be almost exactly contemporary with the casket if the commonly accepted date is correct. This observation, often repeated uncritically, however, requires close inspection.
Comparing shield designs
According to the , five units were stationed in Milan – the , the , the, the , and the . Surviving manuscripts of the seem to provide us with the designs of these shields on the page for the . The page shows seven shield designs, but only five units are named. In other words, even if there is a match, we cannot be sure which shield matches which unit. When we compare the shield designs of the based in Mediolanum with those depicted on the lid of the casket, however, there seems to be very little similarity. What is more, the shields on the are uniformly round whereas we know from several other contemporary sources that shields were also oval, and the Brescia lid shows both! Another scene on the left side of the casket shows David slaying Goliath, who holds a round shield with an off-centre grip, which has parallels in other early fourth-century monuments such as the Arch of Constantine (dedicated in 315) and in a mosaic of a hunter from the Great Palace Mosaic in Istanbul. The shields on the front of the casket are quartered, with an intricate four-pointed star on the oval shield and an off-centre quartering on the round shield. None of the shields match these designs.