Polaroid pair two in one with scaleFor optical experiments -one polarizer is fixed & the other can be rotated having aperture 25 mm & scale 75 mm brass graduated with 360' x 1..

one Polaroid fixed & other rotatable  aperture 20 mm , but without any scale ...

Two identical units each provided with Polaroid disc mounted in a rotatable mount, wtih aperture of 25mm, and a pointer traverses a 75 mm dia brass scale divided into 360° x 1. Size is universal to fit any collimator or telescope...

All metallic with Brass C.P. Slit which can be opened with a fine screwA)               for  Telescope mount with screwB)               do- with micrometer C)          ..

SLIT  DOUBLEAll metallic  Very superior quality.A)            with screwB)            with micrometer              C)          &nbs..