Your Speedmaster could easily have been factory fitted with the 220 bezel, even if the serial is different from the range stated in MWO. MWO is a great reference, but it is not and cannot be the only and absolute truth.
The references in MWO are based on a limited number of watches, which the authors have been able to identify in their research.
My '69 Speedy with 220 bezel, produced in august 1970, is within the correct production date range (Q3 1970), but the serial number 30.588.xxx is below the range identified by MWO (starting at 30589xxx as far as I remember)
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