Yes, selenium meters can be useful, but they are not automatically reliable just because they’re battery-free. Selenium cells degrade over time, especially with light exposure. That means condition depends less on age alone and more on how the meter was stored. A meter kept in its case or behind a protective cover may still be usable; one left exposed on a shelf for years is more likely to have weakened output and inaccurate readings.

So a vintage selenium meter can still work, but it should not be assumed accurate without comparison. If you want to use one to check an old camera’s internal meter, first compare it against a known-good meter or against consistent exposure results. Dedicated selenium meters often came with cases specifically to slow this aging.

In short: selenium meters do degrade, mainly from light exposure, but a well-stored example may still be serviceable. They can be a handy accessory for film users, especially to cross-check older meters, as long as you verify the selenium meter itself before trusting it as a reference.