This is an antique Victorian microscope Polariscope used for polarized light microscopy. Beautifully made of solid brass with precision knurled edges, the Polariscope consists of an upper analyzer, and a lower polarizer. The Polariscope consists of upper and lower Nicol prisms used for the polarization of the light. The Polariscope is in very good condition with normal signs of wear for an antique device.
In use, and as shown in the 2nd photo in the listing, the analyzer is sandwiched between the body tube of the microscope and the objective lens. It normally does not rotate. The bottom polarizer is fitted to the substage condenser of the microscope, and consists of a rotating Nicol prism. The outside diameter of the lower polarizer is approximately 38.6 mm or about 1-1/2 inches.
The upper analyzer has upper and lower R.M.S. threads (also known as "Society Threads" which are standard mounting threads for most microscope objective lenses. This device fits between the body tube of the microscope and the objective lens.
I have personally tested this Polariscope on the antique Victorian microscope shown in the 2nd photo. Everything works as it should and the device works well.
Please note: the Victorian microscope shown in the 2nd photo is not part of this auction and is shown here only to demonstrate the proper installation of the parts of the Polariscope.