Antique 18th century Georgian mahogany cased hydrometer bulbs

Antique Georgian mahogany cased hydrometer bulbs, also known as philosophical bubbles or gravity beads. The circular turned mahogany box with domed lid opens to a velvet-lined interior with nine numbered glass beads (originally 12). They were used for testing the proof of spirit. The inside of the lid has the remains of a paper label and listed the spirits and their corresponding numbers. They were invented by Alexander Wilson of Glasgow in the 1750s.
British, circa 1750 - 1780