A Chinese white ware ewer, Northern Song dynasty

A Chinese, white ware, ewer of an elegant double-gourd form and incised line delineations; from the Northern Song dynasty. Covered over-all, except for the base and inner foot, with a white glaze, which appears greenish where it has pooled.
 
Dimension; 16cm tall.
 
Condition; good over-all, with noticeable areas of missing glaze; a common problem of mis-fitting glaze amongst this type of early white-ware. Please ask for additional photos if required.
 
Provenance; acquired from an old English collection.