A professional who assembles and trues balance and hairspring assemblies used in marine chronometers, using truing ii calipers and watchmaker's tools. Responsibilities include:

• Attaches hairspring to collet, using watchmaker's tools.
• Positions hairspring and collet assembly in truing calipers and bends hairspring to correct deficient truing, using tweezers.
• Attaches stud to hairspring and screws balance staff into balance wheel.
• Trues balance wheel, using truing calipers.
• Fastens balance screws, weights, and timing screws in balance wheel, using screwdriver.
• Inserts impulse and unlocking rollers in assembly.
• Poises balance wheel, using truing calipers.
• Connects hairspring and collet to balance wheel assembly, using watchmaker's tools.