I interviewed Mark a few years ago in his office at DR. I called, set up the day and time, arrived, and found out that no one told Mark I was coming. He was gracious enough to give me 45 minutes of his time, I got the information I needed, got a factory tour, thanked him and left. He had a modest collection of vintage Guild guitars, including an archtop he claimed was the first Guild ever made. He told me about presenting the 12 string to John Lennon ("He was my favorite Beatle. I just walked in. There was no security"), and how George Harrison looked a bit peeved that John got the guitar instead of him. Most of you know the story of me and that Guild SF-12.
Mark was the young thorn in his father's side who pushed him to diversify the Guild line and try new things. His innovations are felt to this day. RIP, Mark.
By the way, Mark had nothing good to say about Neil Lilien. We agreed on that one.