This PerkinElmer Sodium Chloride Prism dates from the mid 1940s. It was part of a Model 12 infrared spectrometer first produced in 1944. When not in use the prism was stored in a glass dome with a desiccant, as moisture from the air would eventually dissolve the prism. Read about these prisms at the University of Toronto Scientific Instruments Collection: https://utsic.utoronto.ca/2014/10/15/spectroscopy-beyond-the-visible-spectrum-the-sodium-chloride-prism/
