17th-18th century A.D. or earlier. A carved jet mount with a facing head of a philosopher modelled in the half round, thoughtful expression with furrowed brow, strong nasal ridge and carefully arranged voluminous beard merging with the side hair; stepped rim. 4.43 grams, 25 mm (1 in.). Acquired in the 1970s. Property of an Austrian private collector. [No Reserve]