It must be admitted that the way containers were secured on deck half a century ago is impressive. No bridges on top of the containers, steel cables crossing each other... I wonder if the ship had sockets for container equipment, twistlocks, etc. in the hatch covers...
Or maybe the containers were simply loaded onto dunnage timber.
However, such improvisation is hardly surprising. At that time, real container ships had only recently started to be built and operated. Methods of securing containers transported on universal general cargo ships were often the result of creative improvisation by deck officers and Stevedor companies.

Have those containers shifted? They don't appear exactly straight