Variable Attenuator Plate, ~0 to >25%, ~1x1.5 cm Clear Aperture

Description

Variable attenuator AR-coated glass strip mounted in plastic frame (may be removed easily),
with a  clear aperture of around 1x1.5 cm.  The attenuation is from close to 0 (no attenuation) to 25 or 30 percent.  These were used to trim the laser power in a HeNe laser-based barcode scanner.
They can also be used as variable non-polarizing beam-splitters by reflecting the beam at a small angle (like 30 percent) and monitoring the reflected and transmitted beams as shown in the diagram which shows their use in a quadrature decoder for an interferometer.  In this way, the relative intensity of the polarized components is not affected much. These are included in my Quadrature Decoder and µMD0 kits.
(Many beam-splitters listed on eBay as "non-polarizing" have a large effect on polarization and tend to be useless for these applications.)
While they can't quite achieve 50:50, it's close enough for most government work. ;-)
Excellent condition.
Thanks for looking,
--- sam