Clausager's original 'King Dick' jack - note the foot with the flat bottom and flat angled tops, and round-topped cover over the gears:

Clausager's replacement 'from the same maker' in May73, note the foot is curved top and bottom, with an exposed gear:

Clausager's replacement 'from Mettalifacture' in Feb 74, note the identical foot to the above, with flat-topped cover over the gear:

My blue and black jacks, almost identical i.e. curved feet and flat-topped cover over the gear, with the same profile of the main upright. Exceptions are the stop pin being on the side of the arm in my blue jack and underneath in my black, also the different shape of the bracket where the lifting arm connects to the screw, both arrowed. The main difference is in the lengths - the blue being 19" overall and the black 20.5", the blue lifting arm being 10" and the black 13":

Crank handle of a basic scissors jack extended by 15" using 'cut and shut' so I can use it from the ends of the car without having to crawl underneath.