In doing some research, I found a cryptic reference to the beef commercial in a newsletter completely unrelated to food.
The newsletter appears to be from, of all things, an advanced life support training organization. On page two of this newsletter from 2004 (note this link will open a PDF file), there was a comment indicating that the city of Windom, MN, was the "home of the beef commercial."
Intriguing. And what a strange way to find out information on a sandwich!
I e-mailed the Windom Chamber of Commerce last week inquiring as to the validity of this claim, and to see what sort of history the sandwich might might have in the area. I am sure that will be one of the more odd e-mails that the Windom Chamber has received, but should they write back, I will report the findings!
Yours in gravy,