Panakaduwa copper plate
Panakaduwa copper plate is a Sri Lankan copper plate made at the request of King Vijayabahu I for a high-ranking general called Budalna (Sithnarubim Buddhanayake (Budalnavan), Dandanayake of Ruhuna). The plate was made in gratitude for the aid that Budalna gave to juvenile prince Kirthi (Vijayabahu I) and his family during his pre-regnal days from the Cholas. The king had triumphed over the Chola ruler and secured his kingdom. It was apparently completed around 1082-83 in the 27th year of his reign. This copper plate can be considered as the world's oldest thank you note in the recorded history.