ASTM mechanical property specification verification tests have been conducted on the 2 /sup 1///sub 4/ Cr--1 Mo steel. The base properties have been determined for the steel at various temperatures and after exposure to various environments. Compression load versus deflection calibration curves have been determined for 316 SS loading rings. Thermal expansivity of both the 2 /sup 1///sub 4/ Cr--1 Mo steel and 316 SS have been determined at 500/sup 0/F and 900/sup 0/F. Thermal expansion characteristics and time dependence of the deflection of ring-sample composites have been measured to provide information about the constancy of stress on samples loaded by pre-compressed rings. Results of all exposure tests, including samples under load during exposure, in inert gas reveal that no degradation of ambient temperature mechanical properties occurs.