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I'm just going on what I found on Velobase (which isn't infallible):
"To confuse issues SR Decided to make these cranks compatible to Shimano Dura Ace or Campy, with differing Crank Tapers to match and possibly differing BCD measurements. To further confuse things, the model type was not stamped on the crank arms - so compatibility will be a matter of trial and error."From that, you may be on to something BCD/taper-wise...
I have a feeling it’s ISO. I think on the SR 80s cranks, 130 bcd was JIS, and 144 was ISO. Will give it a try on my SR bb which is ISO, first.