CASIO fx-82 SUPER. I bought it in 1.992, use it in college, at the university and 20 years more at the office. Never changed battery and im not going to retire it
Casio FX-82 Solar II ab € 14,38 (2022) | Preisvergleich Geizhals Österreich
Casio FX-991EX Scientific Calculator FX991EX FX 991 EX 552 Function for sale online | eBay
Casio Scientific Calculator fx-991ex / fx-991ES PLUS / fx-991MS / fx-82ES PLUS | eBay