Richard, if you need to measure the T.C.s of your assemblies, then your 3458A is stable enough to do that nice volt-nuts project. You only need a temperature stable environment, a precise thermometer (PT100, precision NTC), a 2nd DMM for the thermometer, and data acquisition. I also have done these delicate measurements on Vishay VHP202Z with high stability that way. Also important was the good coupling between the DUT and the thermometer, and also that they were having a thermal mass (alu block and alu case). See Andreas' thread and my setup here: http://www.eevblog.com/forum/projects/t-c-measurements-on-precision-resistors/30/ As this is a relative measurement, this T.C. measurement can be easily done with an uncalibrated 3458A also. After that, it should be relatively easy to find a cheap possibility to measure the absolute value of these reistors at a certain temperature. That would fully characterize the resistors. Frank