The ones I remember had "Port Sunlight" stamped on the sides, with the rays of the rising sun and a lifebelt or Lifebuoy emblem, in red and black I think, identifying the brand of soap and its maker. The bottoms were made of two broad slats, but the sides were strongly jointed at the corners, creating a solid container, rectangular in shape.
I don't know when these boxes went out of use but I believe all the packaging was cardboard when I worked briefly in Pears' soap factory after the war. At all events, prewar soapboxes were very serviceable and quite strong enough to stand on if you turned them upside down. They would raise you some 22 centimetres off the ground, or 9 inches as some members of the Conservative Party might prefer to say.
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