My dad's Casio fx-570 Scientific Calculator from more than 30 years ago, I still use it, the buttons are so tactile and satisfying to press : r/BuyItForLife
Casio FX-7400GIII Graphing calculator Cyan Display (digits): 21 battery-powered (W x H x D) 87.5 x 21.3 x 180.5 mm | Conrad.com
Casio fx-9860 GIII Graphic Calculator, 21 Digit, 8-line 3 Color Dot Matrix 64 X 128 Dots, Grey price in Saudi Arabia | Compare Prices