No, but it can become one. There's a 3V battery in there a little like a squashed penlite if that makes sense.
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You can replace it with a CR2023 or any other similar 3V coincell. A 2023 should last for many years, the smaller/slimmer ones (2021, etc) will work but simply yield less longevity. Personally, I'd remove the existing battery and install a little CR2023 socket but just a couple of wires would do the trick, too.
One thing to pay attention to is that these battery will often read OK or borderline (2.8-3V) or even a little better out of circuit. When testing them with a low impedence meter, the reading drops and the truth is revealed. If you don't have a low impedence meter, not a problem - those batteries are so old, one may safely assume it's had its best years.