Here's one I and probably a lot of people haven't seen before - The King himself wearing Engineer Boots. He's been seen wearing other variations of boots, but not the kind that count. Thanks for another great contribution Warren!
Being a Harley kinda guy, these could be a Harley brand or even a pair purchased from a dry goods store on Beale Street. After all, he has been known to frequent a little shop called Lanskey's.