Kind of makes you wonder what was going on at Dell in 1940-- did someone just say, "Hey, lets try raising the price of a few comics by 50% in certain markets and see what happens?" Seems unlikely, especially since the typical purchasers of comics would be especially sensitive to this sort of increase. What would the reaction have been when distributors/retailers got wind of the fact that the cover price of their comics was increased, yet the prices in other markets remained the same?
If it's been established that these were not Canadian copies is it possible they were printed domestically for sale in some other English-speaking country or an American territory?
By the way, nice copy of FC4, Montezuma-- it sure doesn't look low grade in the photo.