The idea to standardize coins and money appear long before the introduction of Euro. Already in 1865 France, Belgium, Italy and Switzerland fonded the Latin Monetary Union.
This agreement stated that each state had to strike its silver (from 20 cents to 5 francs¹) and gold coins (from 5 to 100 francs) according to common specifications. So these coins could equally be used in any state in the Union
This system had a great success and about 50 other countries chose to strike their own coins according to this specification. United States also thought of joining the Latin Union and created in this view a pattern coin called stella.
Only after WWII, when silver and gold coins were abandoned, the Latin Union had an end.
Such coins were struck for 100 years all around the world. Therefore the Latin Union can be a nice subject of collection.
¹ 1 franc from 1855 is equivalent to 2.60 USD from today.