Shock–wave profiles have been measured by many techniques probing the stress or particle velocity histories of shocked materials. Among the most commonly used methods are the velocity interferometry system for any reflector (VISAR) and embedded foil stress gauges. It is relatively unusual to employ both these techniques simultaneously in an experiment. The gauge is backed using a transparent rear window made of polymethylmethacrylate (PMMA) through which the VISAR is also shone. Examples are given of results from the two techniques for metal, ceramic and glass targets, and the direct comparison validates the accuracy of earlier gauge data. Finally, the results are used to construct the principal Hugoniot of the PMMA window material to high accuracy.