This is most likely the last poster by Grun, and an official commission for the celebration of Joan of Arc's trial in Rouen.

Jules-Alexandre Grun (25 May 1868 – 15 February 1934) was a French post-impressionist painter, poster artist, and illustrator.[1]
Grun's best known painting is called The Dinner Party, produced in 1911. It was, however, in the fields of poster art and illustration art, for which he was famous. He was employed at a large printing company in Paris and his artistic director was Jules Cheret. Cheret was also his main competitor in poster art. (Wiki)

This Poster is published in Grun Posters Book by Israel Perry and Alain Weill , 2005, Page 137

Very Good. A- to B+ Restored paper at the top, color fresh, creases.