Using Euro coins as weights (2004)

Euro coins circulating in various countries of the Eurozone have different obverses – I wonder whether that affects weight?

I was thinking similar, but then it occurred to me that they may be debossed, rather than engraved, so no change to material? Not a coin expert :D

Probably not significantly. It would make it too hard to build machines that accept all euro coin variants, yet reject cheaper non-euro coins of similar proportions.

Any additive/subtractive method at that scale for coin faces sounds like a huge waste of time and effort compared to just pressing the design, but also not a coin expert.

Striking/pressing with a shaped die is the traditional process, not least because the material itself used to be the store of value rather than the provenance of the mint— The coin shape was really there to certify how much gold/silver it contained and that the government had been paid whatever tax (seignorage) was owed on the ore.

Now that we’ve lived in a fiat-currency world for decades, it’s possible that new processes are being used as the concerns are different— anti-counterfeiting measures are more important than anti-shaving ones now, for instance.

The weight is set by law at least to the 10th of a gram. Couldn't find an explicitly set margin of error though

Yes, they stamp/press it and the deformation of that process is also used to fit the inner to the outer part on the 1 and 2 Euro coins.

See this German children's program: https://youtu.be/nBuSmbcp1AE (seems to only have German subtitles, but they are quite visual)