Doctor Who Pinball BackBoxes
12 Test Games were made and tested (in public) with the Bally Style Backbox.
Then the 12 games were convereted to the Williams Style BackBox.
And Doctor Who was the first Bally Game to be produced with the Williams Style BackBox.
I do not know what happen to the orginal BackGlasses

The Bally Style BackBox
(Top to Bottom), The Dalek on Top,
Lower, the Speaker panel (the left/right speakers are the black areas) on top and the 'Magic motion' picture between the speakers.
Lowest down is a full sized BackGlass with the dot matrix display showing through the bottom of the Backglass.
DrWhoBallyBackBox DrWhoBallyBackGlass

Williams Style BackBox
(Top to Bottom), The Dalek mounted on top of the BackBox.
Lower, the Smaller Backglass.
Then lowest the speaker panel with a Dot Matrix display between the displays and the space for Lights below the display
DrWhoWmsBackBox DrWhoWmsBackGlass