Hello Ciggy,
A nice find on your behalf. The Cooper's box is definitely original and I have several in my collection. They contained the smaller Cooper powder containers that actually went in the water when sheep were plunge dipped. By that I mean the sheep were sent through a concrete arrangement and the sheep had to swim their way through it. All the while a bloke stood there with what's called a push rod and dunked their heads under the water.
Those sorts of dips have been banned in Australia for a number of years now because of the arsenic based powders and should anyone use them now the wool is heavily discounted on price as it is pre tested before sale and the arsenic will still come through any old dips that the farmers may be silly enough to use.
Most dips are applied straight after shearing by the farmer using a hand held applicator however some still plunge dip the sheep using contractors who travel from farm to farm.
Regards Rustycutters