Sorry, BCGs are "Birth Control Glasses", military slang for the big, thick rimmed plastic glasses that recruits get issued in basic if they wear glasses. During the 70s the glasses were considered unattractive to the point that nobody wearing them would ever get laid and so served as a form of "birth control", hence "birth control glasses". Though they seem quite popular now.
Okay, round two. In the 1970s in the US, that style of glasses was issued by the US military and considered very unfashionable. I wasn't aware style had changed that much, but then I have the fashion sense of a chimp.
I do not know how you do, we have it in fashion for a long time. I do not care what is fashionable and what is not. I wear what I like. I do not care about the laws of fashion. These glasses have been a footnote to the hipster mem by Ariel.