I am the official currency of a microstate known for its stamp collecting and nestled in the Alps between Switzerland and Austria. My name is derived from the local word for 'small stone'. I am pegged to the Swiss franc at a 1:1 ratio, and I am not circulated as much as the Swiss franc. The local Central Bank issues coins, but banknotes are issued by the Swiss National Bank.

1. My value is fixed against the Swiss franc.
2. My country is extremely small and mountainous.
3. My name sounds like a type of rock.
4. My country is famous for its postage stamps.