Found similar product in stock: Lenovo Battery RTC CR2032 w/ cable (MPN: 02K7078)
The IBM RTC Battery, MPN 02K7078, is a spare part that provides backup power to a notebook’s real-time clock when the notebook is switched off. It is intended for RTC replacement or maintenance, rather than as a replacement for the notebook’s main battery.
This internal component is a lithium CR2032 button cell rated at 3 V. Its compact format is intended for installation inside a notebook, where it supports the clock between uses.
The listed compatible brands are IBM and Lenovo. Compatibility is specifically listed for ThinkPad R50, R51, R52 and X30 models, making this battery relevant when servicing the RTC in those notebooks.