I think I meant 26", not 27" i.e. 650
26"/650c Wolber SP1 tubulars were, I think, marked 571. The difference in size between a a 26" and 27" tubular is more than 30mm in diameter so it should be really easy to just figure out the size from its circumference.
I've edited my post...
@mustard started
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26"/650c Wolber SP1 tubulars were, I think, marked 571. The difference in size between a a 26" and 27" tubular is more than 30mm in diameter so it should be really easy to just figure out the size from its circumference.