Abstract: This invention relates to a copper base alloy with improved toughness and weldability for use in making molds for glass containers. The alloy of the present invention contains copper, nickel and aluminum and may have intentional additions of iron for grain refinement and niobium for increased oxidation resistance. It is felt that niobium should be added when the alloy is to be welded under adverse conditions. The nickel content sould be between about 12 and 16 wt/o and the aluminum content between about 8.5 and 11.5 wt/o. If the aluminum content is above or below the range, and/or the nickel content is near or above 16 wt/o the alloy may have excessive hardness. Iron additions for grain refinement should be up to about 1.0 wt/o. The niobium, when added to improve weldability, should be maintained between about 0.5 and 1.0 wt/o.