A professional who inspects watch balance wheels to verify that rim lies in single plane and that plane is perpendicular to staff axis, using truing ii caliper, tweezers, and loupe.

• Mounts balance wheel and staff between jaws of truing calipers, using tweezers, and adjusts index pointer above end of balance arm.
• Turns and examines wheel to verify that space between index and both arms is identical, using loupe.
• Adjusts index pointer over rim of wheel and verifies that width of light slit between rim and index does not vary as wheel is rotated.
• Rejects wheels that are not true.