20 Korun Československých

Tuzex was the Czechoslovak state-run hard-currency retail network, and these bony — as the vouchers were colloquially known — functioned as a parallel currency for purchasing imported or otherwise unobtainable Western goods. They were never legal tender in the conventional sense; the system existed specifically to capture foreign exchange from citizens who received remittances from abroad or earned hard currency through approved channels.

Holding bony without a sanctioned source was technically illegal, yet a black market in them flourished openly for most of the network's existence, with exchange rates against the koruna varying wildly depending on political climate and available inventory.