This type of composition showing the Virgin and Child enthroned is known as a Maestà (from the word 'majesty'). It was a popular design with Sienese painters.
The painter takes his name from a fresco in Casole d'Elsa, near Siena, painted in about 1317. This Maestà may have been painted around the same time. The painting has been drastically cut at the base, probably because it was damaged. Originally the angels were full length.