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
Reproducibility | Details | Hackaday.io
How to replace a battery on Casio calculators - YouTube
Battery Scientific calculator, Model Name/Number: Fx-82 Ms, Size: Handy at Rs 450 in New Delhi