Mug, East London, England, 1772. Soft-paste phosphatic porcelain marked "RD & MY Tidswell 1772." (Collection of the British Museum BM: 3-4.1. Photo courtesy of A. Gabszewicz. This documentary mug is the type item for the Tidswell period c. 1770 ? 1774 and is characterised by the reintroduction of glass cullet ? both lime alkali and lead glass; see Ramsay and Ramsay, 2007: Table 14. Members of this period tend to be underfired and translucency is very poor to non-existent.