Abstract: Reference standards that include known defects for use in nondestructive inspection are disclosed. In one example, the reference standard includes a metallic body, a another metallic body and a predetermined quantity of a contaminant material. The metallic bodies are diffusion bonded along a seamless interface. The predetermined quantity of a contaminant material has a predetermined composition positioned at a predetermined location proximate the seamless interface. Methods for manufacturing the reference standards are also disclosed. In one example, a method for manufacturing the reference standard includes positioning a predetermined quantity of a contaminant material having a predetermined composition between a bonding surface of a metallic body and another bonding surface of another metallic body. The two bonding surface are diffusion bonded to yield a bonded article (e.g., a reference standard).