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There are various coins made from silver or gold that are also valid currency.

For example all German 10 euro silver coins that were released between 2007 and 2010 are made from 18g sterling silver. <https://en.wikipedia.org/wiki/Euro_gold_and_silver_commemora...

After 2010, the silver price got too high so they first reduced the amount of silver in the coins to 62.5% and then got rid of the silver entirely.

With the current price of silver the silver in the coins is worth $8.158 (it was worth more than 10€ for a while).

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There is also WIR https://en.wikipedia.org/wiki/WIR_Bank which is backed by assets, but I think it's not targeted at individuals.