The printed message says: Is it love or the joy of Spring, that makes the light glimmer in your eyes.
Earlier French postcards (1900-1920) always seem to show men with mustaches. They were favored so strongly that until 1933 the French gendarmes were required to have them! Grenadiers in the French Army also had to wear them throughout the 19th Century. At some point the hairy upper lip fell out of favor. French postcards from the '30s and later all seem to show clean shaven men. In 1975, the French military changed its regulations and specified that military personnel could only grow a beard or mustache during periods when they were out of uniform.
Recently I stumbled upon a mustache blog that added even more illumination to the subject. Pacifists such as the Amish and Mennonites grow beards but not mustaches, specifically to avoid the military associations. Be sure to check out the blog, Mustaches of the 19th Century, for everything you need to know about mustaches.
Now here's a mustache for you:
This is a Turkish card from about 1963. It shows a man who is the world champion of something, though I'm not sure what. He is (was) 52 and weighs 90 kilos and his height is 1,80 meters. I think Biyik is his name. There's a phone number; maybe I should give him a call.