These listings may have solved the mystery.
https://www.worthpoint.com/worthoped...-heilmann-very
"** These Cards all Have REALLY COOL Advertising on the backs-it takes up the Whole Backside.."Save your Coupons for Free Prizes"...Etc..."Lucky Pocket Piece of Babe Ruth, Photos of Tom Mix, Charles Lindbergh, etc.. Exhibit Supply co., Address, cutout coupon... +++ REALLY TOUGH & Desirable/Collectible Issue -"
This listing actually shows the back side with the info.
https://www.worthpoint.com/worthoped...fatty-arbuckle