A highly rare variety.
A sixpence with a type IV bust and an Arabic, instead of Roman, singular in the denomination (V1 instead of V2). However, while this notation is simply rare for thick shields (with double outlines), it is very rare for thin straight shields (R6/R7 on the Kopicki scale, respectively).
In the reverse legend, a characteristic error for this variety - ARGN instead of ARGEN.