If there was a commonly used item today that was going to be our equivalent to the Roman dodecahedron, what item do you most speculate it would be?
The Roman dodecahedron is an item that has turned up in a lot of sites where people do archaeology. While most items, given time, have their purpose easily or at least approximately deduced by researchers, the Roman dodecahedron's purpose is largely baffling to even the most studied of archaeologists, who have no idea on where to start with it. This in turn would probably baffle the Romans, who would have seen it as a common household item, no different from a spoon or a comb.
Suppose a few thousand years from now, archaeologists were excavating our remains and had varying degrees of success deducing what different things were for. If you had to guess what common household item of ours would stump them the most, what item would you guess it would be?
Any electronic device with firmware in flash. The charges will have decayed a long time ago, leaving a paperweight.
Sufficiently diligent far-future archaeologists may dissect and catalogue the devices well enough to develop a taxonomy of components, having their own names for components, CPU architectures and such, but they’d then be left with something like “this was a programmed control device of the Xargx Valley type, variant 13, only with a screen, a speaker, two microphones and a motor actuator. We speculate it may have been a domestic appliance, a children’s toy or part of a transportation device. Alternatively, it may have had religious or ceremonial uses.”
My guess for the dodecahedra is that they're a tool to aid with cryptography. This video explains it well, but TL;DW you'd use the dodecahedron with two concentric circles full of letters, and rotate one to know which letter to replace with which. It's a slightly more advanced and secure version of Caesar's cypher, and I could easily see the Romans doing something like that.
On the other hand I wouldn't expect them to be used for knitting or jewellery, as simpler devices would do the same job.
...but to answer your question, I think that most decor items will give those archaeologists a hard time. Stuff like this:
I was almost going to say "yerba mate bombillas", but they'll likely detect saliva DNA in them and guess that they were used as straws:
I think it's unlikely to be a knitting tool, as you could achieve the same with a simpler tool.
For example, I've seen people saying it's for wool gloves. But a bar with five holes and some knobs would do the trick, no need for an intricate form like a dodeca.
The sleeves from gastric bypass surgery. Lots of other medical devices have an obvious function, thinking of steel hip replacements or screws to bend badly broken bones. But the sleeve might perplex someone thousands of years from now.
This question is tough because I feel that our society has documented everything. Even the smallest item has articles written about it. But if a lot of that info was lost, things like bluetooth headphones might cause confusion. If technology doesn't endure, will future generations think everyone had them to limit surrounding noises when in reality we introduce sound wirelessly.
Not a direct answer to your question, but the book Motel of the Mysteries by David Macaulay is about a group of future archaeologists excavating a ruin from 1985, and is definitely of some relevance here.