Excavators in Central China's Henan Province have found 504 spade coins dating back more than 2,000 years.

The coins, unearthed at a construction site in Sanmenxia, date back to the mid- to late Spring and Autumn Period (770BC-476BC), according to researchers from a local museum.

The coins were preserved in a clay pottery cooker. Of the total 504 coins, 434 remain intact, researchers said.

Archeologists found no sign of ancient tombs at the excavation site.

"It is rare to see such a large number of the coins so well preserved," said Li Shuqian, head of the local museum, adding that the discovery will be significant for studying China's history of currency.

Spade coins were an early form of currency used during the Zhou Dynasty (1046BC- 256BC). They are shaped like a spade or weeding tool. The coins were abolished after Emperor Qin Shi Huang unified the currency in the country in 221BC.