I've looked around and haven't been able to find any definitive information on J. Edgar Hoover's signature. There seems to be more than an ample supply of signed letters of his for sale out there though. I'm not sure if these were secretarial or autopen or J. Edgar's own hand. If anyone could shed some light on this little bit of signing history, as he was the director of the FBI for over 37 years, that would be great. Here's an example of one of those letters, from a year before his death in 1972.