what is mc murdo true identity and how does he reveal himself were there any hints that may have given it away himself ? were there any hints that

We discover that he once took the name Jack McMurdo and was a part of a mafia-type gang in America. It is then revealed that Jack McMurdo was just a cover for Birdy Edwards, a Pinkerton detective. No matter what name he decides to use, he is brave, smart and of good humour.