We checked the square against a couple of others we have on hand and it appears to be true. We found no markings on the item but it does have light scratches. The base is 1/2 inch thick. Please study photos as they are part of the item description. It is sold as found and may need cleaning. It weighs 4.7 ounces prior to including packing materials and a sturdy box for shipping. It is blank and does not have any incremental measurement marks.