A professional who inspects completed hairspring assemblies, using loupe and watchmaker's tools. Responsibilities include:

• Verifies that spring and balance wheel are true in flat and round, and that mass of balance wheel is equally distributed around axis of rotation.
• Examines positioning of parts to determine that parts are in beat, and that overcoil is in specified relationship to spring, using loupe.
• Verifies that parts are securely staked, using tweezers.
• Separates unsatisfactory assemblies.
• Observes minute parts and functioning of parts with loupe.
• May test parts to determine if vibrating point has been accurately located, using master balance.