The caption describes the unit so I won't duplicate here.
I remember seeing this rig in Brisbane at the time and note the artist's omission of the prominently emblazoned "Leyland - She's A Lady" across the front panel right above the radiator grille.
Freddy moved on from the Comet to a couple of Mercedes semi trailers, always on the Sydney - Brisbane run....
I'm unable to acknowledge the artist because his details were cropped in the copy sent to me by Laurie MacBeth.