Rodrigo,
That is exactly what it is. It is obviously broekn as it would have been a full diamond once. The enamel is in
good shape for the
price paid - nicer enamel is quite
rare on these. Enamel colours changes very much with age so it is hard to be sure but the blue was almost certainly blue, the pale rose likely
red, and the middle band might have been yellow or green.
I think these are more likely 2nd - 3rd century based on fact that those are the dates for
fibulae (
brooches) with similar enamel. It is very
rare for 1st century to have such enamel. In 1st century AD heavier, unenamelled seal boxes were the norm. I have unfortunately never heard of a 4th century seal box so I don't know what they are like.
Shawn