Sophie65, sorry but you are wrong, those are centimes 100 centimes = 1 Franc
in 1960 they adopt the new Franc and 100 old Francs become 1 new Franc. 0,40 is 40 centimes ( please note they use the coma not a dot ) Centime = 1/100. The cents come from it; cent in French is hundred
From a calculated guess, the Franc was about 25 cents US at that time, this stamps will have been the equivalent of a ½ cent
DO not confuse Fr with RF and that means Republique Française
Those are not proof but stationary , the margin are way to big for an imperforate.. The color of paper fit with a stationary, I will check later.
here just as reference the stamps for that period ( not the stationary the OP present ) , showing c for centimes and fr for franc

Here how look a 1 franc stamp of that period, they use capital F

Fr was use for old Franc on this 1930 stamp
