on the "Pen" sets (R313, R314, Gold Medal, etc.) gives some info about the nomenclature - Gold Medal Flour was one product in the Gold Medal Foods line, which was produced by General Mills. The cards were advertised primarily as Gold Medal Foods premiums (rather than specific to the flour).
You guys might have an interest in checking out my articles. I haven't talked to Lyman for a while, but according to the site, back issues are still available for individual purchase, or (if you never subscribed) you can order the whole run. They pack a tremendous wealth of information on vintage cards. These articles are in issues 6 and 7.
https://oldcardboard.com/subscriptions.asp