Large mug with Diatom sprigs on outside. Seconds due to the small mark on the front near the sprigs (a dod of glaze). Diatoms are single celled, microscopic, silicaceous algae, often used by geologists and freshwater and marine ecologists. These are freshwater species.  Holds 400ml, which is quite a big cuppa. 8cm tall, 8cm wide. Diatom thumb rest.