[meindnoch]

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.

[tengwar2]

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.