Le Tallec's pieces without these marks are likely to be produced between 1930 and 1941. Incrementation of the dating system was done every six-month period from 1941 to 1991, then every year since.
Le Tallec's pieces without these marks are probably from the period 1930-1941. Dating began with a six-month interval from 1941 to 1991 and then transitioned to yearly increments thereafter.