[achn]

I’m sure this is not an original theory, but when I saw the device i immediately thought that it may be a tool to sort / check the size of coins. Each size lines up to a known gold or silver piece. The largest hole allows all to be removed easily.

[carabiner]

Isn't this dramatically over-engineered though? Here's what they use today: https://static-numista.com/forum/images/58fa1df58e689.jpg

[Cthulhu_]

I was going to say, a flat object (out of wood or metal for 'genuine-ness') would be a lot more practical, and they'd be using them everywhere.

In western Europe, they would use scales to determine the weight of coin, since size itself doesn't mean much - that's logic used by modern day vending machines.

[ertian]

I believe these dodecahedrons come in a whole variety of sizes, and aren't particularly consistent (i.e. there's not 3 standard sizes, just a whole range). That undermines a lot of potential explanations.

[proee]

One of my engineering friends devoted a large portion of his life studying the dodecahedron. He believed it was used as a "fluid scanner" to measure the displacement of 3d objects using water.

https://www.eeweb.com/interview-with-john-ladd/

[piaste]

Oh man, that brings back memories. Roman System Engineering a.k.a. "TimeCube with Tits"! They still have the original promo 'marketing' on Vimeo: https://vimeo.com/29490154

[pnw]

Did anything ever come of it? The interview has some wild claims.

[lostlogin]

Not sure if it adds or detracts from your theory, but coins were sometimes clipped to change their value. I’ve got a silver one that had the edge clipped off to alter its value.

[lapsis_beeftech]

If it was a tool for commerce you would expect them to appear all over the old Roman empire and especially in Italy but according to the article they are only ever found in the northwestern parts of Europe. Also, if the purpose was validating currency the holes would need some markings indicating which hole matches what coin, wouldn't they?

[Pxtl]

Most of my tools around the house have minimal markings, if any. There are a zillion sizes of Allen key, and very few have the decency to mark themselves.

My measuring cups have markings are marked in paint, most of which has already worn away. Wouldn't stand a chance over millenia.

That said, you'd expect at least one or two to have informative notches for sizing. The universal dearth of text for such a common device is surprising.

And also, wouldn't they be a standard size for the region if they were for measuring coin? It sounds like each dodecahedron was different sizes.

[mtdewcmu]

It could have been carried by tax collectors.

[rexreed]

Of all the theories, this seems plausible. Has anyone done that to your knowledge? The easy way to test this is to take an assortment of Roman-era coins and see how well they match up to the holes and ring sizes. The pegs that protrude could easily help not only to stabilize the system but prevent coins from sliding off if placed in a stack.

[shahar2k]

they did mention they appear to be of widely varying sizes... I imagine if the holes were meant for specific coins they'd all have matching sizes...

I like the idea that the ratio between the incoming and outgoing holes allow you to get correct angles while looking through regardless of how the object is held (look through one of the smaller holes hold it far enough that the larger hole matches, and you have an exact angle viewer)