This is a very good English "RUMMER" Drinking Glass, which were originally drinking glasses used in English taverns in the late 18th and early 19th century.
The glass is hand blown and made from heavy lead glass, having a soft greyish colour. It has a large "ogee" shaped bowl, over a basal knife knop, leading to a short thick solid stem with a good thick square foot. The square foot is more uncommon and a nice feature of this glass.
Dimensions:
Rim diameter 3.55 inches
Foot 2.3 inches square
Height 5.2 inches.
Overall a good late 18th century English rummer.