 Silver pennies of roughly this weight (1–1.6g) were to remain the sole unit of English currency until the 13th century, with the exception of rare silver halfpennies and even rarer gold coins.The first ('primary') "sceattas" of series A, B and C were largely confined to Kent and the Thames Estuary, though the emergence of the 'secondary' "sceattas" (probably c. 710) introduced a breathtaking array of new designs and saw minting expand to many new areas