Originally Posted by
Andy_K
I thought only Italian used 70mm bottom brackets.
I've seen more than a few Japanese bike-boom era frames with 70mm shells and English thread.
That said, I have one bike with Italian threads and a 68mm wide shell, so as has been pointed out the design is flexible.
Italian track frames used to have 65mm shells, and bikes with stripped English or metric (French or Swiss) thread shells can be re-tapped to use Italian thread.
So, you should not really have any confidence that shell width will tell you anything about the shell thread spec.