Casio watch. Had it for ~20yrs. It died today but I just replaced the battery and it's back again! I had only changed batteries twice: 10 yrs ago and today. Truly BIFL
How to Change a Watch Battery
HOW TO] : Remove the Casio watch Module 2359 (DataBank ABX-xx) | WatchUSeek Watch Forums
Removing a Watch Battery from a Casio Watch from WatchBattery (UK) Ltd