Casio - FX-82MS. I bought it in high school, used it in University and now on my 4th year as a Professional Accountant. Haven't changed the battery once. : r/BuyItForLife
CASIO FX82MS Advanced Scientific Calculator for A-Level & Gcse's 2 LINE DISPLAY | eBay
Fx-82Ms battery changing - YouTube
Buy Casio Scientific Calculator FX-82MS-2 For Engineering Students Online at Best Price|CasioIndiashop.com