On my classic 1970s bike I have a Campagnolo rear hub marked ITALY 35x24F, obviously an Italian thread. When I removed the Atom/Maillard freewheel, I was surprised to read FRENCH M34.7x100 on the back. How did a French thread freewheel fit in the Italian thread hub? This freewheel had been installed on my bike by a reputable dealer and former racer himself. Is it possible that he made such a glaring mistake? I should mention that I was able to remove the freewheel effortlessly.
Later, out of sheer ignorance, I mounted a Regina Oro freewheel marked F.I, so obviously an English thread. That freewheel also went on the Italian hub effortlessly. Because English and Italian threads are supposed to be semi-interchangeable, that shouldn't be a huge surprise (I have some trouble removing the freewheel now, because the Regina two-notch system is rotten). I still don't understand how both a French-threaded Atom and an English-threaded Regina fit on my Italian-threaded hub just fine.