Originally Posted by Iride01

Not thread direction. But different thread standards. Even if the threading is the same diameter and pitch, whether it was French, Italian or English might be different. And the bike the country was made in might not be a good determinant of whether it is or isn't. Things were changing between the late 60's to early 80's for bikes then. As the increasing international trade made manufacturers realize that they needed to agree on something so that a part made in one place will fit any bicycle made elsewhere.

I only know that some old Regina FW's aren't standard threading. Maybe another member here knows for certain.