Polishing kit

Hinged wooden box with white metal clasp and plaque inscribed 'POLISHING KIT PK-01 RESEARCH & INDUSTRIAL INSTRUMENTS COMPANY ENGLAND'. The box is divided into compartments holding a synthetic sponge, two synthetic bottles, two felt lined wooden frames, three glass blocks, a velvet strip and a metal mechanism for holding the velvet taut; also contains instructions for use. The kit was used for polishing rocksalt windows. Salt windows were ground against textured glass surfaces until flat and free of scratches then polished with velvet stretched across a glass block.