In about 848 both mints switched to a common design known as Dor¯b¯/Cant – the characters "Dor¯b¯" on the obverse of these coins indicate either "Dorobernia" (Canterbury) or "Dorobrevia" (Rochester), and "Cant", referring to Kent, appeared on the reverse. It is possible that the Canterbury mint continued to produce portrait coins at the same time. The Canterbury issue seems to have been ended in 850–851 by Viking raids, though it is possible that Rochester was spared, and the issue may have continued there. The final issue, again at both mints, was introduced in about 852; it has an inscribed cross on the reverse and a portrait on the obverse. Æthelwulf's coinage became debased by the end of his reign, and though the problem became worse after his death it is possible that the debasement prompted the changes in coin type from as early as 850.