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.
The works by Le Tallec, lacking these identifiers, were likely created between 1930 and 1941. The dating system was updated every six months starting in 1941 until 1991, after which it changed to an annual increment.