A coin measurer is still my goto explanation. Especially with most models having an inset for the coin to rest on / fit in. The hole itself is then just to quickly/easily get the coin out again with your finger.
With so many different coin sizes and types in the empire, I think this makes most sense.
Wikipedia also mentions this:
> Several dodecahedra were found in coin hoards, suggesting either that their owners considered them valuable objects, or that their use was connected with coins — as, for example, for easily checking coins fit a certain diameter and were not clipped.
If you look at ancient coins, you'll see that they didn't have identical sizes. They were minted from a standard weight of metal, but the manual minting tools of the time couldn't guarantee precise thickness and shape like we have today with machine-made coins. So a dodecahedron with precisely cut circular holes is not a good way to check your coins.
Also if they did have identical sizes and there was a need to measure those sizes, we would expect a lot of much simpler devices to measure them - say a flat piece of metal with differently sized holes. Fancy versions like the dodecahedron might exist, but they would be outnumbered by the utilitarian devices.
With so many different coin sizes and types in the empire, I think this makes most sense.
Wikipedia also mentions this:
> Several dodecahedra were found in coin hoards, suggesting either that their owners considered them valuable objects, or that their use was connected with coins — as, for example, for easily checking coins fit a certain diameter and were not clipped.