Wasn't there an "Order 67" switch too? I genuinely can't recall if that was something I read in one of the Legends EU books, or on a message board. There was order 66 to attack the Jedi and order 67 to attack the governing body and who knows how many more there could have been, if there were more?
Edit: I guess I could google that. And here is what I found:
https://starwars.fandom.com/wiki/Con..._1_Through_150
So, yes, in the Legends it existed, but Order 65.