Yep. Karl von Mueller and Deek Gladson were both pen names. He re-worked his wife's first and maiden names to come up with the "Deek Gladson" one. You'll also notice that most, if not ALL, of his books were copyrighted in his wife's name to insure she would have control of all of his materials should something happen to him. When some low-crawling piece of dog crap burned down his small office building at his place, most of his reference materials went up in smoke. I believe that the Valley of Secrets mine / cave / cache was the main project he was working on when his health failed. That's a big reason why he moved to Segundo, CO.
I got to actually meet the man only once, but I read everything he wrote, that I could get my hands on. I even bought a bunch of copies of that old mining journal he published years ago, from a treasure hunting shop in OKC about 16-18 years ago.