Made up (from components from other controls) for the film production Finding Neverland, where it can be seen during the opening credits. It was more recently used on the Disney live-action Dumbo. 
Useful for demonstrating colour mixing concepts.

Notes: 
The Lock offs do not disengage (or declutch) when you reach the top or bottom of dimmer travel. You have to unscrew them when they reach end of travel. 

This board is marked up to use sequential dimmer numbers, but earlier versions would have used geographic dimmer labelling (based on location within the theatre). 

Black labels + / - a third (750W +/- a third gives you 500W or 1000W load), with a different dimmer curve. Other dimmers were wound for a specific wattage. 

Switches - Battleship switches - 3 position double pole. Extra spring-loaded switch. 

• FULL ON
• OFF
• ON DIMMER

Bracket Handle
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Bracket Handle
Click thumbnail to enlarge