Common: readily available at most large militaria shows or easily found for sale on the Internet or in "surplus" stores.
Available: harder to find but usually available if you know where to look and are patient.
Scarce: occasionally seen or offered, but may be difficult to find in US due to limited sources.
Rare: rarely seen; usually available only from other collectors or in Russia.
Very Rare: perhaps not one-of-a-kind, but rarely seen even in the USSR during the Cold War period.