2 Antique Clock Keys Fits Schatz 400 Day Anniversary. Size 1 Chime Clock Key. This is a new brass single end size 1 chime clock key. The hole diameter is 2.50 mm. New French Clock Key Size 1. This is a new French pattern clock key size 1. This is used to wind French clock mainsprings. It is steel, plated with nickel. The hole measures 2.50 mm. We work hard to update our descriptions and pictures of our merchandise. As part of a process of ongoing innovation by our suppliers, newer versions of the item shown may be shipped before we are able to complete an update. As a result there may be a slight variation in color and design.