Commonwealth (1649-1660), AV Unite of 20 shillings. 9.02 g, Dated 1660, mintmark. anchor, 

THE COMMONWEALTH OF ENGLAND, shield of St. George in wreath, mintmark anchor above.
GOD WITH US, shields of St. George and Ireland, value mark XX and date 1660 above. 

North 2716, Seaby 3209
Extremely rare. 

Sold by Spink - Auction 16014, Lot 471, March 2016.