Casio FX82 calculator I bought in 1982 at the age of 15. Used it throughout school, my apprenticeship and work as a draughtsman. Don't use it much now but it still works
CASIO FX-82LB Fraction Scientific Calculator Retro Vintage For Work School | eBay
Kenko Scientific Calculator fx-82LB : Buy Online at Best Price in KSA - Souq is now Amazon.sa: Office Products