The single coinage design created a form of monetary union in southern England, reinforcing the mingling of economic interests between the two kingdoms and the military alliance against the Vikings. Coin hoards in Wessex dating to the earlier period of separate coinage designs have few non-Wessex coins, but after the adoption of the common Lunettes design, coins of Wessex and Mercia were used in both kingdoms, and even in Wessex hoards coins of Æthelred I form a minor proportion of the total. Between one and one and a half million Æthelred I Regular Lunette coins were produced, but this seems to have been significantly less than in Mercia. It is not known why the Mercian design was adopted, but it probably reflects the fact that the Lunette type had already been used for more than twelve years, the simplicity of the design, which could easily be copied, and the greater strength of the Mercian economy. The bulk of surviving Æthelred I coins are of the Regular Lunettes design, with 118 coins struck by 21 moneyers, six of whom are known to have also worked for Burgred; the coins are notable for consistency in design and good quality of execution, and they were mainly produced by Canterbury moneyers, with a few in the Mercian town of London. Only one coin is known which was produced in Wessex itself. There were also Irregular Lunettes issues, one of which was a degraded and crude variant, perhaps a result of a breakdown in controls at the end of Æthelred's reign, when Wessex was under the pressure of Viking attacks. Alfred kept the Lunettes design for a short period following his accession in 871, but the design disappears from hoards deposited after around 875.