Bought new for about £150 which was the cheapest I could find it (after a lot of searching!) but then I found out it probably wouldn't work in my Thinkpad so this has never been used - still has the protective film on it.

You can check the specs here: https://www.panelook.com/ATNA56WR14-0_Samsung_15.6_OLED_overview_49382.html

In addition to checking dimensions, eDP version etc. PLEASE ensure you are replacing a similar 4k Samsung OLED as they apparently use their own eDP pinout which is different from the eDP standard. If you're replacing a panel which isn't a Samsung OLED the 40 pin cable will physically fit but probably still not be compatible with this panel and will almost certainly blow your motherboard's backlight fuse or worse which will require repair.

Please check this link for where I first read about this (thankfully before trying to install) and ensure you are replacing the same sort of Samsung 4k OLED panel: https://community.frame.work/t/oled-option-for-display/28864/23