• Although ISO & BSA are officially interchangeable they are not identical (BSA is 1.37" and ISO is 1.375") - same pitch.
    I'd imagine a 'dale would be 1.37" and a campag BB 1.375"

    No, for several reasons.

    There might be a colloquial usage of BSA for some cycle threads, but the 1.370"x24tpi BB (and sprocket) thread is correctly called BSC (British Standard Cycle) not BSA (Birmingham Small Arms)

    This exact dimension was adopted by ISO

    There is no 1.375" BB thread, although 35mm French and Swiss thread are approximately this size. Italian 36mm x 24tpi threads are the same pitch as BSC, albeit with opposite hand on the drive side, but at ~1.42" they are very obviously bigger, there's no way you'd mistake them when offering up an Italian threaded cup to a BSC BB shell or vice versa.

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