That letter, in Bo's own hand, is all the provenance you could ask for. The letter is also interesting in that Bo did not cross out the "JR." on the letterhead. My guess is that Bo's father was still alive in 1964. Both had the initials W.D. but Bo's father was not Walter Doane and thus Bo was not a junior. To help keep the mail separate they decided that Bo would use "Jr." in his correspondence.