Any good examples to convince me? I have 13 generations of Croatian money from the Austrian-Hungarian time till the modern Kuna
You are confusing fiat currency with money. It's understandable why you would confuse the two because the governments of the world have replaced money with fiat currency and led everyone to believe it is money. We call it "money" out of habit but it's not. Not anymore.
Here are the properties of money:
Medium of exchange
Unit of account
Store of value
Divisible
Fungible (two pieces of the same weight have the same value)
Durable
Portable
Fiat money, especially paper currency is somewhat durable, but does degrade over time. Fiat currency is not a reliable store of wealth because the value of every fiat currency in history eventually went to zero.
But you asked for an example, so I'll give you one. The Spanish Milled Dollar became the universal "Money" of the New World and was actually the first world wide international currency. The consistent size, weight and purity made it the most reliable coin in the New World (similar thing happened previously with the Thaler in Europe).
Long after the Spanish Empire was gone from North America, the Spanish Milled Dollar (Officially called the Peso by the Spaniards, worth eight reales) was the standard money in North America. It didn't need a government backing it. Hell, even the pirates of the Caribbean used it as their standard currency. ("Pieces of Eight")
To enact the Coinage Act of 1792, when the United States decided to come up with a standard One Dollar Coin ("Dollar" is actually English for "Thaler") Alexander Hamilton took a batch of circulated Spanish Dollars, got the average weight, and set that as the weight of the Silver Dollar. That's why a U.S. dollar was a little lighter than a brand new Spanish Dollar. Spanish Dollars circulated along side of U.S. Dollars as official U.S. currency all the way up until the Coinage Act of 1857.
A Spanish Milled Dollar NEVER lost it's value because it was real money.
A little bit of trivia about the Spanish Milled Dollar:
Smaller coins were fairly rare, so to make change people would cut larger coins into pieces (remember the "Divisible" part about money?). Since cutting a coin by halving it, then halving the halves, then halving the quarters was the most convenient way of cutting it up, the large coins were worth 8 reales which made it easier to make change. The smallest practical division of a coin was an eighth, and that was called a "bit". So if you divide a Spanish Dollar into eight pieces, you get eight "bits" - each worth one Reale. Two bits are a fourth of a dollar. Ever heard a quarter called "two bits"? That's why.
Here is the original "quarter" worth two Reales ("two bits" in America)
Notice that "S" shaped scroll around the column?
Looks kind of like this: $ Doesn't it? That's no coincidence...