This is a 6" Air Sander Polisher - Model PIM501
It's a pneumatic (air-powered) Dual Action Sander + Polisher.
What is it use for?
For smoothing and shining surfaces - mainly for car bodywork and furniture work.
It does 2 jobs in one:
1. Sanding:
When a panel beater repairs a car or a carpenter makes furniture, after filling with body filler or putty, they need to sand it smooth. They stick sandpaper disc (6 inch / 150mm) to the yellow pad and use this machine to sand fast and smooth. The 6mm eccentricity means it doesn't leave scratch marks - orbital motion.
2. Polishing:
After painting a car, to make it shine like new, they put the orange sponge foam you see in the picture on it. Then with polishing compound, they use it to buff and polish the car paint.