Double entendre. Flash was a French magazine that featured this cancan photo on the cover of one of its issues. This photo is from a French site where you can purchase this issue if you wish:
http://www.journaux-collection.com/recherche.php?&qu=FLASH&co=&ti=&num=&da=&ta=&de=&av=&new=&disp=&aff=&pa=9
