James Kent; Prince William Ware
The last plant of the original works of James Kent (Old Foley, Longton) was demolished in 2006. We know Kent from the Old Foley piggy bank models, one mould 11 cm long with different patterns and colours. About the date of the Old Foley piggy banks there is hardly a rule to be given.
The Prince William Pottery is now known as Britain's Premier Mug Decorator. PWP made piggy banks in the 1960's. The curator told me that they have no more production records or old moulds. The PWP piggy banks are painted on the glaze, which is easy to brush off.
New Devon; Holkham
About the New Devon Pottery I could find no data, except that they were specialized in souvenirs. The hallmark has a beaver in it (from 1957 on). The piggy banks can be distinguished by the peculiar coin slot, all of them are 11.5 cm long.
The Holkham Pottery (Wells-next-to-the Sea in Norfork) was founded in 1951 by the wife (Elizabeth, Countess of Leicester) of the fifth Earl of Holkham and produced pottery until September 2007. The piggy banks are 11 cm long.