More info for you.
Miche used to have some decent 650c wheelset for sales, but don't think it's available nowadays.
Thanks! I did see the Sheldon page but gave up at the "so the nominal 650 mm designation is now more theoretical than practical" bit in confusion!
Miche at least gives me something to google
TL:DR - 650b is the largest, and 650a is the smallest (by a small margin).
@Brookly_Bay started
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More info for you.
Miche used to have some decent 650c wheelset for sales, but don't think it's available nowadays.