About 100 bronze Roman dodecahedrons dating from the 2nd and 3rd centuries A.D. have been discovered since the late 18th century, but no one can agree on their purpose.
Here's a list of possible functions of the mysterious objects, compiled by Big Think:
- A specific type of dice for a game since lost to history.
- A magical object, possibly from the Celtic religion. A similar small, hollow object with protrusions was recovered from Pompeii in a box with either jewellery or items for magic.
- A toy for children.
- A weight for fishing nets.
- The head of a chieftain's scepter.
- A kind of musical instrument.
- A tool to estimate distances and survey land, especially for military purposes.
- An instrument to estimate the size of and distance to objects on the battlefield for the benefit of the artillery.
- A device for detecting counterfeit coins.
- A calendar for determining the spring and autumn equinoxes and/or the optimal date for sowing wheat.
- A candle holder. (Wax residue was found in one or two of the objects recovered.)
- A connector for metal or wooden poles.
- A knitting tool specifically for gloves. (That would explain why no dodecahedrons were found in the warmer regions of the Empire.)
- A gauge to calibrate water pipes.
- A base for eagle standards. (Each Roman legion carried a symbolic bird on a staff into battle.)
- An astrological device used for fortune-telling. (Inscribed on a dodecahedron found in Geneva in 1982 were the Latin names for the 12 signs of the zodiac.)
The "knitting tool specifically for gloves" seemed unlikely to me, but after watching this video of someone using a 3D-printed replicate to knit a glove, I'm less doubtful.