An ingenious and beautifully made device consisting of a folding solid brass frame housing a circular lens that lines up with a 1 inch square cut out. Designed for magnifying fabric to calculate the threads per square-inch. Generally, the higher the thread count of the fabric, the better the quality. Circa 1910.
Dimensions (when folded up): 4 cm/1⅝ inches (width) x 5.5 cm/2⅛ inches (depth) x 1.5 cm/⅝ inch (thick).
