Lovely example of a 19th century Frog mug.
These were often found in 17th/18th century taverns, were used for drinking typically cloudy beer. These mugs were part of the tradition of drinking games such as fuddling cups and puzzle jugs.
Inside the vessel, lifelike three dimensional frogs or toads are positioned at the bottom, seemingly attempting to escape! They slowly emerge at the bottom of the vessel as it is drained and cause great surprise for the unsuspecting drinker and hilarity for the audience!
This example is in Majolica; Bamboo and Ferns, with two little frogs lurking inside.
 
Dimensions: Height 11cm, Width at handle 12cm, Diameter at base 8cm