07-026. American, late 2nd quarter 20th century, with metal label on the base stamped "REFRACTOMETER, GEMOLOGICAL INSTITUTE OF AMERICA" and serial numbered 264. Made of black enameled casting metal, 4 1/4" long x 2" wide x 5" tall, with illumination porthole in the back, lead glass hemisphere in the top with knurled knob at the base to rotate the hemisphere, pivoting eyepiece on the front, and internal refractive index scale 1.30 - 1.85. This earliest G.I.A. refractometer model is in very good overall condition, in its original fitted leatherette covered wood case.
