Every part on ChronoShop has been on our bench. Calipers, optical-comparator, photography, provenance trace. If it can't be installed in a serviced movement and run within tolerance, we don't list it.
This is unfashionable. Most parts catalogues list everything that arrives, photograph it on a sheet, and let the buyer sort the wheat. We refuse — not for marketing reasons, but because we sell to people who service watches for a living, and a wrong part costs them four hours and a customer's trust.
The grade on each plate is recorded against a written standard, not a feeling. The standard is published. If a part is sold below grade, it ships back at our cost.
— House rule, since 2018