Get a 12v fan, or some sort of something you can put a bit of a load on the cell. We had a d7500, that would hold VOLTAGE, but, the second we hooked up a small fan to the posts, the voltage tanked, meaning there was a dead cell in there (or two).
If it holds voltage, and can hold a load, who cares how old it is. Run it. But, i would check it before installing it. Good luck.