ETA Caliber 2640

The ETA caliber 2640 is a small ladies size handwound movement with 17 jewels and a frequency of 3 Hz (21,600 beats per hour).

2640 VS 2660:

There is a similar caliber 2660 with the main difference being that the 2660 has a higher beat-rate of 28,800 bph (4 Hz).

Parts Interchangeability:

Many components are interchangeable between the 26XX family of movements, but it depends on the beat rate and calendar complications, etc. For example, the complete balance (with regulator and Incabloc) for the 2640 is part number 721/2007, and the packaging also lists calibres 2641, 2648, 2650, 2651, 2657, and 2658. NOS packaging will cross reference the compatible calibers for the part, but you will want to double check before ordering from your watch parts supplier of choice.

Additional Resources:

• More ETA watch movements