Item is an early 19th century brass oil lamp. It features a removable fuel chamber with a spout where a length of wick would be fed through. When in use, the second spout would catch drips from the wick. The bottom of the lamp has a weighted base for use on a table, and a hook at the top so it could be hung against a wall.
This style of lamp was popularized by the Dutch and is known as a Snotneus lamp, which translates to nose-drip, and refers to the double spout design. Sometimes called whale oil lamps, they were typically used with animal fats.