The Unique metalique pieces as found in this section deserve a bit of attention because these really represent a different line of pottery.
Ever since the Zuid Holland Pottery (the PZH) started, pieces had to be produced faster and faster to keep them at a reasonable price level.
Unique Metalique pieces however were bucking that trend, instead of producing pottery at a faster pace they introduced even more steps into the process which of course slowed down the rate in which these pieces were produced. Apparently it took 4 times for each individual piece to be fired in the oven before it was finished. The painting itself became more involved, different and more costly types of paint and glaze with metal oxides, as well as different application techniques were used. The final burn was the most special, because at that time they reduced the available oxygen in the oven which resulted in a more distinct metalique look. Not only did it take longer to produce these items but also the cost associated with the paint and glazes was much higher than otherwise.
So in short these pieces costed about twice the normal costs of production, but it did produce an article with a completely new look and feel.
Not many people were involved in the making of this type of pottery so the production was nowhere near as high as it was in the 1920's. This time only a handful of people were educated and skilled enough to produce these pieces.
Experimental versions of metallique pottery exist from the Porceleyne fles ( from 1892 to 1914) and also from the PZH (around 1925 to 1936). But none of these were as refined as the ones produced from 1943 - 1953.