The R Polariscopes Model No. ACM-P-2604 is a gemological instrument designed to determine if gemstones are single or double refracting, aiding in the identification of moissanite, strain in diamonds, and distinguishing synthetic from natural gems. It operates on the principle of plane polarized light and can analyze various optical characteristics of gemstones. The document also provides detailed instructions on how to use the polariscope, along with its applications and specifications.