 Incrementation of the dating system was done every six-month period from 1941 to 1991, then every year since.By 1978, date of the transfer of the atelier from Belleville to rue de Reuilly in Paris, the date mark starts by R (for Reuilly), then the letter.By 1995, corresponding to the new installation at the avenue Daumesnil in Paris, the date mark starts by D (for Daumesnil) then the letter.