No batteries. As Young He mentioned, selenium meters don't age so well, old Westons that don't work are far, far more common than ones that do.
If it does react to light at all, you might be able to use it by compensating, but it's probably not worth the effort, especially since they continue to degrade, so you would need to calibrate your compensation factor regularly.
I have a Gossen selenium meter which was dead accurate when I loaned it to a friend a few years ago. I got it back recently, and it's a couple of stops off, and I expect that it spent most of that time in a drawer, away from light.
But, on the bright side (not an intentional pun), those old Westons are pretty to look at.