Most certainly a "French thing".
Peugeot bikes used this type of attachment, I've seen several. Not sure of the time frame, but I'd say late seventies to early eighties models.
Ed
<classicrendezvous@bikelist.org> Sent: Sunday, January 13, 2002 11:25 AM Subject: Re: [CR]Simplex/Spidel Question....
> Many thanks for the fast responses to my question!!
>
> I have never seen a bike so equipped with this type of boss for this type
of
> derailleur, but it would seem there must have been more than just a
> couple......is it a "French" thing?????
>
> Cheers,
>
> Chuck Brooks
> Sunny in Malta, NY