Omega 300 (R 17.8), Main spring, no: 770

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  Manufacturer: Prima, no: 130 J 29

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  Fits cal: R17.8, 300, 301, 302, 310, 311

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  H: 1,30
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  D: 8,5
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  F: 0,09
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  L: 290

Versions:

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  R17,8: sub second, rhodium plated bridges, to 1949.
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  R17,8AM: sub second, antimagnetic, rhodium plated bridges, to 1949.
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  R17,8SCAM: center second, antimagnetic, rhodium plated bridges, to 1949.
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  300: same as 17,8, sub second, rose gold plated bridges, from 1949.
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  301: same as 17,8AM, rose gold plating, from 1949.
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  302: sub second, incabloc.
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  310: same as 17,8SC, from 1949.
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  311: same as 17,8SCAM, from 1949.