MWO is a great reference, but the findings are based on research of a (limited) number of cases (watches). The range of serial numbers for the 220's stated in MWO represents the lowest and highest serials the authors have been able to identify in their research for the book. It does not nescessarily mean that watches with lower or higher serial numbers are incorrect. My 220 has serial 30.588, which is below the range identified in MWO, but it is a genuine 220, produced in august 1970. Conclusion: Research is only research, not the ultimative truth [emoji4]
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