linen tester

== English == === Etymology === From linen +‎ tester. === Noun === linen tester (plural linen testers) A folding magnifying glass which, when unfolded, forms a frame for the lens at a pre-focussed distance. Commonly used in stamp collecting. A small magnifying glass, as might be used to check the thread count of linens. === References === “linen tester”, in Merriam-Webster.com Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.