I just read a RawStory article about Jim Jordan's idiotic response to the photo the DOJ released showing the Top Secret documents found in Trump's "beautiful house". In the story the author mentions that some documents bear the notation TK, which the author explains stands for TALENT KEYHOLE, a keyword designation for satellite and spy plane collected intel.
I'm going to guess that TK has since been declassified, because in my day revealing what that means was illegal. That was my field.

@Jeber I know the *name* has been declassified. The content itself I doubt has.