After seeing this sign on the back wall of the ex-Ford, ex-HDT workshop slowly deteriorate l finally got around to snapping a photo. The sign is visible from the train just on the Melbourne side of Auburn Railway Station.
Harry Firth added to the rear of the building after the Cortina GT500 program circa 1966 and l'm guessing the sign was painted at that time. He can't have thought it important or necessary to remove it after the swap to Holden and HDT in 1969.