5 Korun

Tuzex was Czechoslovakia's state-run hard currency retail network, and its bony — the vouchers it issued in exchange for Western currency — functioned as a parallel monetary system that quietly acknowledged the koruna's inconvertibility. Foreigners, diplomats, and Czechoslovaks who received remittances from abroad exchanged their dollars or deutschmarks for bony, which could then be spent at Tuzex shops on imported goods entirely unavailable through normal retail channels.

The 1984 series was printed by STC, the same Prague facility responsible for official state banknotes and postage stamps, which explains the relatively sophisticated security specification for what was technically a retail voucher. Possession of bony by ordinary Czechoslovaks without a legitimate foreign income source was legally ambiguous — tolerated in practice but occasionally used as a pretext for prosecution.