I believe Mark Modano who wrote the book you are referring to is now deceased. I knew Don Washington and think he was still plunking around the Great Lakes that early on, although I do not knowm when he became active on the FL scene. Craig Hamilton would be my choice but that is just an opinion.
Two people who might know are Dick Holt (he ended up with a lot of the McKee family photos and used to run the Somewhere in Time Treasure Museum in Isllamorada) He's retired but still should be listed around Islamorada.
Another person you might want to send a photo to is Ron Nelson. He was friends with Art McKee and might know. He is in his 70's and not into the new-fangled technology of computers, emails and such but you might drop him an old fashioned letter and a copy of the photo as he would be happy to help if he knows the answer.
Ron Nelson, 218 Trinidad, Tavernier, FL 33070
GH