This is a microscope illuminating lamp typical of the early 19th Century. The lamp is supported on an articulating arm screwed to a heavy brass base. Two set screws allow the support arm to extend. A third set screw allows the lamp to be tilted.
The lamp consists of a central oil lamp and reservoir. At the top is the cloth wick and chimney. Flanking the lamp, at flame height, are a plano-convex condenser lens (dia=5.3cm, f=4.5cm), and a concave reflector (dia=5.8cm). The condenser lens is backed by a blue glass filter. The lamp base is 7.5cm tall, the chimney is 17cm tall.
It probably burned Sperm Whale Oil.