Linen Tester 10X power 23mm square metal frame.
A linen tester is a strong magnifier with a built in measuring scale.
Originally the linen tester checks the quality and measure the number of threads
within a certain area of fabric.
Today, it measures line width and check the registration of color separations in the
field of printing and publishing. The scale is usually divided into metric millimeters.
Linen testers are also used in other branches of industry.
For example, they can be used to measure the line weight of barcodes as well as
agriculture for spotting microscopic bugs in fruit and maize crops.