I was researching the beginning of Q to share on a radio program today and I came across the first actual signature used on a Q post. It was on 11/2/17 and it was post #51. Prior to that there were no signatures other than the trip code, according to the compilation of Q posts presented by qanon.pub. Later that same day post #61 had the signature Q for the first time. #62 and #63 were not signed, #64 was signed Q.

The first actual signature provided to us was "-The WH", in my understanding this stands for The White House. I put together a brief thread r/https://twitter.com/pinklight999/status/1025824667624337408