Which currency is stable over time and not subject to inflation?
None.
The reason why is simple: Every currency is:
Historically, the gold standard secured against effects of inflation and deficit spending. It was guaranteeing the value of the currency. So, logically, many people think all we need is the gold standard and most of the economic problems would be a thing of the past.
More importantly, we also need to focus on how to take away all the tools the governmental, quasi governmental organizations and public collectivities have to manipulate the economy.
It is also necessary to prohibit deficitary budgeting and hidden government or public loans, obtained through the national currency.
In my humble opinion, The Solution to Inflation is
a GOLD BACKED and NON GOVERNMENTAL CURRENCY.