I was 23.....my one and only time....(sigh). Now I get asked if I'm a senior citizen, eligible for a discount....(tears falling down my face). *~*
When I was twenty-one (almost forty years ago) my aunt asked me to pick up some cigarettes for her at the store. They carded me (even then, you had to be eighteen). My reply was "If I have to get out my ID, I'm going back to get some beer and make it worth the effort."
Throughout my thirties and forties, I was always mistaken for someone ten to fifteen years younger. Now, my almost totally grey hair gives away my true age.