I just purchased about nine proofs (near perfect condition) in that date range for $10 on average,
The 100 schilling coin from 1979 issued by Republik Γsterreich zu Wiener Neustadt is an Austrian commemorative silver coin. The value of the coin would depend on its condition, rarity, and demand among collectors. However, as a rough estimate, it could be worth around $20 to $30 USD.