Goliath PSU connector cable

[Borgy]

Hi - does anyone have a clue as to what the pictured cable is for/needs to be attached to?

I was cleaning up said Goliath PSU and noticed that one cable behind the on/off switch was not connected. Is it potentially earthing??

Unit works fine with cable unconnected but seems odd.

 

[demolition]

Green/Yellow is earth and it should be connected to the chassis.