New 5 Sided Clock Key Mainspring Winder Clockmakers Winding Tool

This is a new 5 sided clock key. It is used to wind clock mainsprings.

The sizes are:

• Size 2, 2.75 mm
• Size 4, 3.25 mm
• Size 6, 3.75 mm
• Size 8, 4.25 mm
• Size 10, 4.75 mm