Casio fx 31. Dad bought this during his college days in 1978. Running flawlessly since 41 years now. I use it sometimes when I'm bored of using my phone. : r/BuyItForLife
CASIO FX-31 VINTAGE Calculadora científica Año / year 1978 Vintage Calculator EUR 238,99 - PicClick IT
calculators/Casio fx-31 - calculator.org
Vintage Calculator Casio FX-31 Green VFD - YouTube
Calculadora Cientifica Casio Fx 31 | MercadoLibre 📦