This is an Architect 24 inches and four-fold rule, hand made especially to order, from the highest quality of Ivory. The end plates, hinges and joints are artistically made from German silver (a silver-white alloy of copper, zinc, and nickel) and Electrum (pale yellow alloy of gold and silver). The 3 hinges have a center steel bearing. The inside ivory edges are beveled and have 8 architect’s scales. The main hinge is a protractor.The ruler is signed Robson 45 Dean St. Newcastle on Tyne. Frederick Robson opened his shop in 1866. He was also an optician.