Hi George
The lot of four that recently sold on Ebay included the envelope. The envelope's return address was Gold Medal Foods. The stamp was a precancel from Minneapolis, Minnesota. The addressee was to a person in Ohio, which makes sense when you consider that the four cards were Indians. I think it is safe to attribute this issue to Gold Medal Foods. Whether they were a Wheaties premum or not, I don't know.
http://www.ebay.com/itm/1934-Gold-Me...p2047675.l2557