My fav was Casio fx 260 solar: https://www.amazon.nl/Casio-Solar-Scientific-Calculator-Black/dp/B000Q5XTBQ https://www.amazon.nl/Casio-Solar-Scientific-Calculat

My fav was Casio fx 260 solar: https://www.amazon.nl/Casio-Solar-Scientific-Calculator-Black/dp/B000Q5XTBQ https://www.amazon.nl/Casio-Solar-Scientific-Calculator-Blac... indestructible. small. solar (never out of battery; worked also with indoor electric light). contained all I needed for school (im from before the graphical calculator era).