It seems that the hood lights with Marchal/Cibie lens were originally made at the request of Citroen for the DS. As a French car company, Citroen was encouraged to work with both French light suppliers and avoid exclusive deals.
This is what a Cibie heir explained to me last week. Often the "hardware" part of driving/fog lights in the Sixties and early Seventies were shared by both brands and only the lens changed. Facing competition from Bosch, both brands eventually merged first under SEV Marchal and then Valleo.