Omega 240-770, Main spring

• Manufacturer: Prima, no: 120 G 20

• Fits cal: R13.5, 240, 241, 242, 243, 244, 250, 251, 252

• H: = 1,20 mm.
• D: = 7 mm.
• F: = 0,08 mm.
• L: = 200 mm.

• 17 jewels, manual wind.
• Size: 17.50 x 13.50 mm.
• H: = 3.25 mm.
• N: = 21 600 A/h.
• Power reserve: 46 h.

Versions:

• R13,5: until 1949, 15 jewels (1939).
• 240: after 1949, 15 jewels (1949).
• 241: 15 jewels, antimagnetic (1949).
• 242: 17 jewels (1944).
• 243: 17 jewels, antimagnetic (1950).
• 244: 17 jewels, incabloc (1950).
• 245: 17 jewels, flat balance ring, 19800 A/h.
• R13,5SC: until 1949, 17 jewels, center second (1940).
• 250: after 1949, 17 jewels, center second (1949).
• 251: 17 jewels, antimagnetic, center second (1950).
• 252: 17 jewels, antimagnetic, center second, incabloc (1951).