That’s the date it was issued apparently by request. This is a certified copy dated Feb 1964.
I'm not sure what "copy" means here. To me this looks like a document created by typing onto a printed form using a manual typewriter. So in the highly unlikely event that it is not a forgery, a clerk probably typed the information from the birth registry onto a 1964 form, that had the 1964 terminology. Or am I missing something?