Those are objects from the Roman Empire. About 130 have been found in total.
They are typically made of brass and fit in the hand but can vary from 35 grams to a kilo. Each side has holes of different sizes with rings around them. On each corner you will find a sphere protruding.
But there are three things you won't find.
- you won't find them in or near the capital. They are found all over the European part of the empire including Britain, but never once in the Near East or African portions of the empire and also never in what we call Italy today.
- you won't find why they exist. There is no known use for them that survives scrutiny. But you will find lots of speculation.
- you won't find any markings. No labeles, no symbols, no gauges, or numbers. Just holes with rings.
Are they part of a mystery colt, some rather expensive game piece, blacksmith training? No one knows.
Find a 3D print file and make one yourself and ponder it for a while. Or draw one. I haven't found any woodworking plans. Maybe I could fix that.
Micron, A5.
Notably, they're primarily found in Gaul and Germania, suggesting that they're not Roman, strictly speaking.
The ones in Germania have almost all been found in the Roman bits of Germania (i.e. east of the Rhine), and Roman Britain is the other big area for them, so it does seem like they're at least partially Roman. They seem to be called Gallo-Roman dodecahedrons a lot of the time because of the areas they're found in, though
These don't start showing up until the 300s CE but those areas were occupied since 100 BCE. So that's a 400 year gap. And they are always found in the presence of Romans, not indigenous locals.