There was a Guggenheimer Distillery in Cincinnati in about 1900, but the better known name is Guckenheimer, which is still around as a blended whiskey brand owned, I think, by Heaven Hill. If it was the cheapest stuff you could find, chances are it was a blend. Guckenheimer was originally a Pennsylvania straight rye.
There also was a Canadian distillery called Gooderham and Worts, which might well have had a brand called Mill Farm. I'm tending to favor that theory, or even that somewhere along the way you substituted "Guckenheimer" for "Gooderham." Canadian whiskey would have also been a good cheap choice in the late 60s.