I looks like what's in there is the original battery. About half of all Crystal Versions I've seen/had these days have dead or near-dead batteries. So to anyone curious, I'd say that there's a 50% chance that the game still saves, a 40% chance that the battery has enough juice to keep a save file for your whole play-through, and a 20% chance there's enough of a battery to keep the in-game time accurate.