Consigned for sale by a UK dealer, the 2in (5cm) pieces, one of a boy beating a drum, the other with a cat, had been catalogued as '19th/20th century'.
Several phones and a bidder active via the-saleroom.com battled it out until it eventually sold for £150,000 to the latter, reported to be an anonymous buyer from China.
Together with the scarcity for agate carvings of boys and the tenacity of Asian buyers, many of whom were in attendance for the two-day series in Salisbury which included the Luís Esteves Fernandes collection of Asian art, the vast price has led the auction house to believe the pieces are far earlier than they had thought; probably 18th century.
The buyer's premium for the sale on May 23 was 22%.
Results and further highlights from the May Asian series in London and in the regions will be covered in a forthcoming issue of ATG's weekly printed newspaper. Subscribe here.