What are the Anaimangalam Chola-era Copper plates Netherlands is returning to India after 300 years?

Issued during the 21st regnal year of Rajaraja Chola I, the plates record the donation of the village of Anaimangalam, near Nagapattinam in Tamil Nadu, and surrounding lands to the Chulamanivarma Vihara, a Buddhist monastery.

Original source: Zee News