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
Amazon.com: Casio Fx-82es Fx82es Plus Bk Display Scientific Calculations Calculator with 252 Functions
Casio FX-82ES Plus Blue 2nd Gen Non-Programmable Scientific Calculator | eBay