The 1939 catalogue released by the Inter-State Nurseries of Hamburg, Iowa, USA. has some interesting information. The catalogue features 9 Cannas that year, including Canna 'King Midas''. Inter-State Nurseries were America's largest direct-to-you nurseries, or so they claimed in the catalogue.
What is immediately apparent from the photograph is that this is not an Italian Group cultivar, see how the labellum (lip) is smaller than the staminodes. The stamen is normal sized, and not as large as the Italian Group varieties. Also, there are no red spots in the throat. The whole red stamen and style are also unmistakeable. We, at Claines Canna, have a cultivar we imported from Turkey that is identical to this, and is called C. 'King of Gold'. That name is translated directly from the Turkish, and I believe means that we have the original C. 'King Midas'.
I have long suspected that what is currently being sold as Canna 'King Midas' was incorrectly named and it is pleasing to find such evidence. I can see no difference between the misnamed Italian Group specimen and Canna 'Austria', and it looks like another misnaming from the early 1980's in the USA.
In Greek mythology, Midas or King Midas (in Greek Μίδας) is popularly remembered for his ability to turn everything he touched into gold: the Midas touch. The picture above emphasizes the golden colour and it is obvious that if it had been a paler yellow, like the current misnamed Italian Group specimen, it would not have been given this name.