Someone who knows about these things has said ...
a) The mark "Cristal St Louis France" (in a circle and with upper case letters) was used from 1952/3 through to the 1970s.
b) There was then a gap, when the "SL" mark (in a circle with double horizontal lines through the letters) was used.
c) However, a similar mark to the first one, but saying "Cristal France Saint-Louis" (all upper case and with "saint" fully spelled out) was used from the 1970s.
d) And there is evidence of the first mark still being used and certainly for the 1992 St Louis 225th anniversary series of items called the "Botticelli series".