DUFOUR BOLTING CLOTH folding magnifying glass

Here is the post of the magnifying glass that I have, as the information below shows it is used to count the thread/hole sizes in cloth or mesh.

this magnifying glass is stamped "made in France", has the mark of the "DUFOUR BOLTING CLOTH", and inside the folding case is the name "BARRY WEHMILLER St Louis". when the magnifying glass is unfolded you would slide the cloth or mesh through the case and count the thread/holes size.

I took the following except from: http://www.angelfire.com/journal/millrestoration/artifacts.html#anchor693392
"Artifacts Found in Early American Mills, making it look more like a real mill. by Theodore R. Hazen"
Every mill would have different types and sizes of paddles. There were ones used in flour and meal bins, bolter bottom hoppers, and in greasing gears and cogs. Flour machinery companies and others that sold only bolting cloth and screen passed out small (usually made of metal) hand held scrapers. They could be used in bolters for cleaning the screens, removing caked on build-ups, and for scraping down the reel surface clean when applying new bolting screen and webbing. Sometimes they are found with a small round magnifying glass (used to count opening in bolting screen) in the round hang up hold hole.....I need to mention hand sifters or as they are know by their traditional name of temse. This is a hand sieve for dressing flour to make it fine, in hand sifting. A mill would have several hand sifters with different size mesh for sifting different materials out of the grind. This is one of the oldest methods of sifting or bolting flour.....Later companies that sold bolting screen and cloth would make sets of small round (usually metal) testing hand sifters. They either came with one round side with a removable ring that could hold on different circular pieces with different meshes, or came in a set of hand sifters with different meshes already set into them. These little test sifters were not intended for the production of flour. The idea being that if the miller wanted to produce a new product, all he had to do is use the test hand sifters and once he found one he wanted order the size mesh for his larger bolter. This became important with the roller mill's gradual reduction system where you might have a lot of very fine mesh bolting cloths.

Picture 4 :Peter A. Dufour, of Dufour & Co. , invented a loom in 1830 which created a sturdy square mesh and revolutionized the bolting cloth industry (American Miller and Processor, Volume 49, 1921). This catalog provides 23 examples of "Extra-Heavy Double-Extra Heavy Silk for Centrifugals and Plansifters", showing varying degrees of mesh coarseness.