Million Miler 300 info?

Can anyone identify which airline (and when) used a promotion of their Million Miler Club, that would match the image on this old set of steel embossing dies? I have a collection of approx 50 old aviation embossing/stamping dies. The general feel of them seems to place them in the 1950s? But the dies and images range from aircraft companies, airlines, WWI planes, old flying boats, and Zeppelins, up to WWII aircraft and even one (futuristic fo the 50s) Rocket