HK469336477
It is a battery with a built‑in “AVT” (Automatic Visual Test) indicator that shows whether the battery is still good or needs replacing. This kind of battery is commonly used in safety or industrial systems to ensure reliable operation. However, without more details, that's speculative. If you have more context—like the device it connects with, a photo, or where you saw it—I’d be happy to help you track it down more precisely.