Up to one billion francs’s worth of 1970s-era bank notes are nearing their cutoff date, when they will unceremoniously make the switch from reserve currency to antique wallpaper as their value is wiped out unless the Swiss government intervenes.
Switzerland is unique among rich countries because its bank notes—from the 10-franc bill all the way to the mighty 1,000-franc bill ($1,025)—lose all of their value 20 years after they are replaced by new ones. The series from the 1970s was replaced in 2000, so their value vanishes in 2020. Franc coins are always usable.
–Brian Blackstone “Switzerland’s Old-Money Problem: One Billion in Expiring Francs” The Wall Street Journal