It was an X-Sense DS31, looks like it has been replaced by this one: https://smile.amazon.com/X-Sense-10-Year-Battery-Detector-Photoelectric/dp/B075Z2MCFM https

It was an X-Sense DS31, looks like it has been replaced by this one: https://smile.amazon.com/X-Sense-10-Year-Battery-Detector-Photoelectric/dp/B075Z2MCFM https://smile.amazon.com/X-Sense-10-Year-Battery-Detector-Ph...