Known. The team found a tall stone doorstep covered in writing.
It belongs to the palace of King Adad-Nirari III at Nimrud, about 30 kilometres south of Mosul in Iraq. The stone is from the ninth and eighth centuries BC. This king ruled from 810 to 783 BC. The doorstep is about 2 metres high. The letters are wedge-shaped, and some are bigger than a whole clay tablet. The words list kings in his family. The stone stayed whole through later attacks on the city.
The page does not say what is still argued.
https://www.ancient-origins.net/news-history-archaeology/nimrud-palace-0017641