It's a graded paper but that's about all I know, it should have another number like 532/2 which indicates the grade. All the Lumiére adverts I have are pre-WWII when they were selling their colour plates and roll films in the UK.

I worked with someone in the mid 70's who's French mother was a member of the Lumiére family, I know he had much archive material but I've not bumped into him in recent years.