This very interesting boxtyp only exist because in the summer of '69 they thought Lesney might offer the very same model with Regular Wheels as well as an Superfast version of it. The "Superfast" version was ment to be just a feature like the "Auto Steer" function already offered on a few selected models. To be able to sell both versions in the same box they had to modify the existing "F" box by removing the "Auto Steer" Symbol ( as the box might come with an Superfast model and hence no such function ) but could also not print "Superfast" on it in case it contains an Regular Wheel model!

Only three such hybrid boxes exist: 15D, 33C and 50C. On the cars the blue sides were showing the old Regular Wheel drawing on one side and the Superfast drawing on the other side!