According to extensive research, this piece seems to be a very rare one. Produced sometime in the early 20th century by the renowed AG Thornton Ltd. Appointed to contractor to Her Majesty’s Government during the early 20th century, Thornton excelled in the design and development of new drawing equipment with many patents and design awards. This rare piece has no patent number on it, it may be a proto-type. Missing a srew on one side, otherwise in fantastic condition for it’s age. Measures: 10cm x 10cm.