I had no idea that they were so common, here in the US I don't see them very often and didn't see them often in the past, so I always take note when I do.
BTW, here's a pic of a late (early 80s?) version with integrated hanger courtesey of miamijim's excellent Peugeot site, this version had the dropout adjuster screw that threaded thru a "trapped" black plastic plug (not shown in this pic):