The Case was a mould or set of moulds in which the production moulds could be cast in plaster.
Using the block mould from the previous process,  a resin case was made of each mould part.
Cases varied in complexity; one for a basin was in two parts whereas one for a toilet was in up to eight parts with additional loose pieces to help to create the shape of the bowl. The more complex the design, the more expensive the process. For complex shapes, rubber inserts could be used to assist the removal of the mould from the case.
Resin cases could be used up to 7,000 times but thinner resin cases although durable could suffer from heat distortion over time with distortion in the subsequent moulds.
Until the 1980’s cases were made in plaster but they had much shorter working life producing perhaps only 500 moulds they became damaged and required replacement.