Audouard riders did seem to love their checkered suiting, checkered millinery and checkered hosiery! By Gad, I would last about 20 seconds in clothing like that before lightly poaching myself in my own sweat.
I am sure that the 21K milestone also had some deep significance - but I have no idea what it was. Le Chemineau used a milestone as their head badge - so perhaps Audouard is rolling regally past Le Chemineau - but if this is the meaning there is no obvious explanation for the ‘21K’.
Perhaps it was simply 21km from St-Étienne to the finest gentleman’s outfitter in the département of the Loire.
(Source gallica.bnf.fr/ Bibliothèque nationale de France)