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Looking at the specs here (below) I would venture that the /S was a vacuum advance unit (those 2 additional part numbers are for vac advance unit & bracket) - otherwise identical. An 'A' suffix usually stands for 'auto advance'.
The 40224 or 40224/S was specified as a service replacement for a number of different parts of similar specification, most likely they differ in drive gear fitting details but highly likely they can be made to fit a Seven.
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